In answer to what you're saying, firstly, I find it fucked up to call it identity politics. People don't want animals to be abused, and so they call it out and post about it like they do for other news.
Anyway, I'm a leftist. I don't really consume right wing media and I don't engage with those communities. And as a leftist it hurts me to see other leftists give a pass to someone like Hasan because it's just giving ammo to people on the right, and when it's such a large community it can make a big stain and push new people out. Not to mention no one should be given a pass. Like, Hasan fans will literally bend over backwards to defend it and act like a cult. Dude has already made several excuses and finally landed on "she wasn't even wearing a collar", even though you can see it in the vod; but if you post screenshots his fans will say it's photoshopped. I'm not good enough with words to convey my feelings on this phenomenon and my distaste for those people. There's more to mention, but this comment is large enough.
Finally, in answer to your last paragraph, it's a fair point in general, but in my case I'm a vegan.