pigeon, I know that this is a problem for you. And I am sensitive to it. But personally I have just straight up not seen this kind of behaviour. If I had ever been exposed to it, I would censure it, and call the person saying it out, and not consider them on the same team as me. But given that I haven't had the opportunity, I don't know what else I can do.
The closest thing I can think of is that people sometimes criticized Clinton for relying entirely on identity politics to define her 2016 brand. But that's a strategic concern, and an accusation of hypocrisy.
I won't live in your country full-time until next fall. And I probably won't be able to vote for a couple of years after that. So I don't want to try to explain to you what your own country's politics are or claim that things aren't happening when you say they are.
But I am interested in this stuff, my fiancee is American and my (hypothetical, mixed race) kids will be too. So I do care and I do want to help the cause of American leftism. But other than, like, eggs on Twitter I don't know where the anti-idpol-leftist phenomenon comes from.