It's not about alt-right humour - which, yes, is usually brutally unfunny for the same reasons ideological jokes are so terrible. What I've also seen around in other places like SA is a strong implication about the dangers of humour making 'alt-right' ideas palatable.
There's this strong paranoia in these kind of SJWs about the seductiveness of other political positions. It's part of why they're hellbent on deplatforming all these people they disagree with and call Nazis. They think that if they're not hardline against every Pepe, every problematic joke and meme that veers from the message, that people might start to listen - and then they might agree, and then they're the enemy.
SJWs aren't considered the new evangelicals lightly. Their behavioural patterns map incredibly closely, right down to the dark allure of the Devil requiring eternal vigilance. Just in this case, the Devil includes such things as satire, dodgy comedy, and an awful lot of pictures with Impact font on them.
It becomes ironic when you consider that half the time when SA mods probe/ban your account, they drop "sick" memes in the reason as well.
Most SA posters, and SA staff, wrestle with a truth that they don't fully comprehend, yet understand well enough to ban any wrongthink -- and that is that their ideas are unpalatable, unpopular, and not mainstream. They know they never will be. They also know the only way those ideas survive is in the face of heavy handed moderation, which is part and parcel for B&R, Resetera, and any other similar board.
They're so close to self-realization. FAU has called right-wing ideologies weeds that need to be stamped out. And he's right, they are. They're pervasive, hardy, and represent all the endurance that his own ideology will never acquire. SA groupthink, and the ideologies that underpin it, cannot, and will not ever survive in the free market of ideas. They don't stand up to the scrutiny of reality and application.
I'm still amazed, above all, that SA posters completely manage to bury their heads in the sand in a world flourishing in populist and nationalist waves, not realizing their attempts at total destruction of these movements, instead of working with them, only make them stronger. And poor, delicate Rich's patreon has to suffer for it.