Sigma, you're right. Singular artists on Tumblr have no power to put up oppressive structures on their own. I have never even attempted to argue they do. However, they can contribute to them, add to them and perpetuate them. And that is something that's actually more harmful than just getting harshly-worded critique and bluntly expressed negative sentiment over said bigotry. I reject the notion that, for example, whitewashing and calling out whitewashing are on the same level of harmfulness. (Not necessarily what you're arguing, but the general sentiment is something I've seen people earnestly espouse.)
However, there's a difference between the aforementioned and actual sustained harassment, which is obviously bad. That's, for me at least, where the boundary of worrying about the feelings of bigoted artists is. Harsh critique OK, hate in moderation OK (if they were doing it inadvertently and stopped after pointing it out, that's a good place to stop), actual harassment, doxxing and suicide baiting and slander and such NOT OK.