He doesn't directly call them Vegan ISIS, he says other people would call/view them as such. Which is basically true if you watch Fox News at all (even if it's not right, of course).
There are a few issues with the premise, but the strongest one.
Wouldn't Fox News do the same regardless?
See their current stance against BLM. If they don't have something... they, just make something up.
Essentially, you're according that segment as a rational actor willing to stand against facism and nazism
but only if collective action is never violent (which, to be quite honest, can be difficult to pull off in large groups where tensions are quite high.) You are more likely to have a rally about civil rights potentially than one about say, climate change, or regulation of the banks.
Like, step back for a second. If your choices are a group that openly marches on killing you or actively hurting you (you as a person directly in this example), that occasionally turns to violence, or a group that fights against that idea that occasionally turns to violence, which side do you support? Logically, you ask neither side to be violent, but one is calling for your death, so you wouldn't support them or stay neutral right?
As I've said before, a civil injustice is not good. Simply on the moral face of it, standing and doing nothing in the name of pacifism doesn't make you a better person. If you support BLM and their aims, except when one chapter goes astray here and there, then do you really support them?
I could see if perhaps you joined a different group with similar aims, but for many, it seems like they're just looking for reasons to disengage from having to deal with an argument at all. If someone breaks down my window for some reason, in the name of stopping facism, I'll want that person arrested, given a day in court, and restitution made to me for damages. But
I'll still also be against nazis, because there's no "both sides", unless side #2 also has the stated aims of segregation, genocide, and hate. I can understand saying, "hey, this isn't the best look, be better", but it's tempered by a heavy, heavy degree of "Hey Starbucks guy, why are you okay with nazis or standing idle while nazis work?"