You don't have to be a centrist to believe Stalin was bad- a hell of a lot of leftists always did, too. Nothing ever justified anybody acting as if everyone on the Left was responsible for Stalin, or Mao for that matter when he emerged.
Why do you totally refuse to acknowledge that there has always been a sizable independent Left which rejects both Marxist-Leninism(Stalinism) and the kind of viciously antisocialist, antidemocratic nothingness Keir Starmer's right-wing British Labour Party supports now and that was supported then by the absurdly reactionary Friedrich Ebert- the alleged "social democrat" who spent his entire first day on the job as Chancellor in 1918 trying to get ahold of Kaiser Wilhelm in the hopes of begging the Kaiser NOT to abdicate, as if it could ever be decent for a non-total reactionary to plead that a bloodsoaked near-absolute monarch stay in power0 the Armistice should have meant the death of all monarchies and empires, including the one fronted Battenbergs in the UK- the same Ebert who had turned the SPD into effectively a party of the militarist right by pushing it to back the Kaiser and the German military aristocracy on the totally unjustified war they insisted on helping start, as all European monarchies and France played an equal role in helping start.
In 1919, Stalin wasn't running anything yet and it wasn't a certainty that the Russian Revolution would produce anything like him- the original program was actually anarcho-syndicalist and the original program- workers control of the workplace, the soviets as actual democratic decision making bodies in which everyone had a real say- remains valid- there was no justification for the Bolshevik getting rid of those things and setting up a dreary, ultimately blood-soaked police state in their place- and had Germany gone socialist in the early Twenties, the paranoia and siege mentality that produced Stalinism would very likely not have existed, meaning Stalinism could have been prevented, and also likely meaning Naziism would never have been a threat. A Left Germany would also have been able to withstand any pressure from Stalin to mold itself into a replica of his essentially neo-tsarist state, and would have created the breathig space for left parties throughout Europe and the world to create models totally independent of the USSR and its degraded ugliness.
And any Left government that came in in Germany in the Twenties would have been massively preferable to Hitler coming to power in any case- no Left government would have staged the Holocaust and a Left Germany- even one that was led by the KPD, and the emergence of a viable alternative to what Stalin did to the USSR could very well have brought him down in the 1920s, replacing him with a humane, democratic and genuinely radical alternative, so, yes, it was silly to do "horseshoe theory" there and imply that the Nazis and those trying to stop them were equally bad.
Agreed about the pact in 1939, as is essentially everybody on the Left today- most of us also believe Stalin betrayed Spain, caring more about stopping the independent libertarian socialist revolution going on in Catalonia than he ever did about stopping Franco and his allies- but the Pact is a tragic pact of 1919- the crushing of the radical democratic alternative to both Stalinism and "social democracy", and of Stalin's obsession with crushing the radical democratic socialist alternative in Catolonia- it was never the only thing that COULD have happened, and it never justified centrists instantly recognizing and normalizing relations with Mussolini's Fascist Italy in the 1920s, Hitler's regime(on "anticommunist" grounds) from 1933 to 1939-i.e., until it it was too late to matter and the success of Hitler's extermination project was guaranteed- and Franco from the moment he rose against the democratic Spanish government- itself largely "centrist"- in 1936.
We can fairly conclude that fascism and the Holocaust were the products of "horseshoe" theory.
I'm not saying never question anything anybody else is saying- any person with a mind, and that includes all of us on the Left, does so on the daily, and as you can see from my posts, I do this constantly as well- the point is that that the center has no claim to inherent intellectual superiority or problem-solving capacity than anybody else- and the smugness and dismissiveness of centrists has caused as much damage as anyone else's strong convictions
Centrists were the ones refusing to stand up to the antidemocratic and bullying tactics of the "Red Scare" types in the post-Great War era AND in the late 1940s, and centrists caused the massive reduction in political possibilities we saw in this country after 1948 or so by pandering to the redbaiters- a step which was especially absurd given that there was never any real possibility that the Communist Party would take over this country.
Centrists were the ones who spent years refusing to actively support the Black Freedom Movement, waiting years after you saw what those monsters did to Emmett Till, until massive numbers of Black people had been killed, buses full of Freedom Riders had been set ablaze, little girls blown to bits in a church in Birmingham, Medgar Evers shot in front of his own family Cheney, Schwerner and Goodman found buried under that earthen dam before they were willing to take any real stand at all, and all the while telling Black people they OWED it to them, the white centrists, never to fight back against their assailants- and then centrists felt perfectly entitled to condemn the Black Panthers for deciding that Black America didn't owe it to white America to die with defending itselt at all.
Centrists waited years to do the same when Chicano farmworkers were being beaten and in some cases killed, before they gave that cause- or the Indigenous cause- even the most timid support.
Centrists spend years in the Sixties saying nothing about our involvement in Vietnam, even though they knew from the start that the war was unwinnable and pointless- and a lot of them helped keep the war going by helping LBJ impose Humphrey as his successor to the presidential nomination in Chicago- even though Humphrey had shown no measurable support in the primaries and almost 70% of the Democratic primary vote had gone to the peace candidates- knowing, as they did, that they were dooming the party to defeat and the country to Nixon.
Centrists spent years in the Sixties, Seventies and even Eighties NOT supporting the anti-apartheid movement- solely because the African National Congress had some Communist members and solely because its program would have done some very mild wealth redistribution from the white minority to those who created the white minority's wealth- until the ultimate centrist, Bill Clinton, forced the ANC to abandon everything in its program that was even mildly redistributionist, any higher taxes on the white rich, even any significantly increase spending on education, housing or healthcare for the majority, while forcing the ANC to pay the debts incurred by the apartheid government in its decades of repression against the majority- a step which was little different than it would have been to force Holocaust survivors to pay the Nazi debt- a debt which, unlike the debt Free South Africa was saddled with, was totally forgiven by Western financial authorities in the early 1950s.
And it was centrists who spent years endorsing the right-wing canard that Sandinista Nicarague was a hardline Communist hellhole- spoiler alert, it was never like that- and, while occasionally voting against the Contra death squads the Reagan Administration funded and largely invented, enabled the passing of such aid by refusing to challenge the Reagan narrative and by making all the sanctimonious comments about "democracy" and "free elections"- the Sandinistas had held and won a free election in 1984, a result which should have ended US hostility to that country- and cheered when the Contra war and the continued US embargo against Nicaragua succeeded in pressuring that country into replacing the Sandinistas with a right-wing austerity coalition.
And, of course, there was the quintessential "centrist" candidate of all time- Walter Mondale, the supposed "Hubert Humphrey liberal" who ran, in 1984, not on a pledge to reverse Reagan's cuts, not on leaving Central America alone, not to oppose the nuclear arms race or end Reagan's unnecessary escalation of the Cold War- an escalation which could have got us all killed- not on any promise to stand up for all the people Reagan had targeted for hate and exclusion but on...wait for it...raising taxes to balance the budget, a policy that benefited...well, no one at all really, an a policy that was never going to lead to anything, and blockade of Nicaragua exactly like the one we've pointlessly maintained on Cuba for sixty-two years now.
I could also mention the "centrist" Democratic Administration of the Nineties- the one which endorsed the entire white supremacist narrative about everything bad in this country supposedly being the collective fault of Black people, the racialization and othering of the poor(culminating in the "Democratic" presidente's disgusting decision to sign that hateful, bigoted, punitive "welfare reform" bill with a big, ear-to-grin smile on his face, while flanked by two BLACK women on welfare- there was no decent reason for him to insist on using the signing to endorse the claim that welfare use/abuse and Blackness were one and the same- who were posed exactly like enslaved humans on an auction block.
That's where "centrism" has gone, Max. That's all on people like you.