If you had looked at the link of this post, you would have read:
Twitch specifies this is conditional: you’re allowed to discuss the political movement of that name, but not “attack or demean another individual or group of people on the basis of their background or religious belief.”
I.e. nothing is masqueraded here as long as they keep to this. This seems to be a reasonable policy. I've seen a couple of instances of people being derogatorily called zionists just for supporting the people of current Israel not being pushed away out of their now decades-old homes, which is hard to still call Zionist if they don't support any further expansion and any offensive military action.
There's almost never anything gained to use "Zionist" on someone as if saying "asshole".
From the link of this post that you could have clicked on: