Well the guy in the tweet himself is making terrible false arguments for no other purpose than to divide the left, so it's pretty fucking easy to believe that he would defend authoritarians.
You can be committed and firm on your issue without being a raging asshole about it at the same time. Most of the vegan communities I've come across don't even talk about being vegan, it's just finding more ways to shit on non vegans.
It's always amazing seeing people react to the 4channiest of 4chan shit with outrage like it's new, why are you even reading greentexts then?