We're not talking about a whole nation- actually, the UK is THREE whole nations and a quarter of another nation (as of now, though it looks increasingly likely that Scotland and Northern Ireland will be leave the UK soon, and clearly should since it does them no good to stay within it) but in any society with social media, widespread violent online comments are a marker that there is something heavily racist and fascist afoot in the cyberland).
There is no context that could justify the host of a live tv show threatening a guest with violence- especially a guest, as was the case w/this young man, who had already faced legal consequences and apologised- and being cheered on for this by a large part of his audience, especially when the person being incited against is there to apologize and take responsibility for his actions, as Mizzy did.
The host had a responsibility to keep his cool and NOT fan the flames of hate- especially when it is very likely that what he said about this young person of color could lead to harm being done to others of the same race who had nothing to do with Mizzy's actions. He failed in that responsiblity, failed to be the grown-up. So did everybody who cheered him on online.
Mizzy is a young person who did some stupid things, as many people who lived to get social media attention have done. He is eighteen. His brain is not fully-formed. He is capable of learning and growth and of addressing whateer inner pain and emptiness within him drove him to these choices.
Treating him as a nasty piece of work who should be dismissed and cast aside and treated with nothing but scorn until the day he dies, a person deserving of violent retribution for childish pranks he has apologized for, achieves nothing.