No, you're here, right now, making the argument.
> If you don't think you've made three hateful statements in one comment then you haven't been paying attention.
You're going to have to do more than type the word "racist" or "transphobic" to explain why the things I've said are transphobic or racist. I'm quite aware of the words I chose and the groups I chose. If you have a legitimate grievance as to why my statements were transphobic or homophobic, please explain. But short of that I have to believe you aren't commenting in good faith.
> Opinion and group identity are mutable
Sure. But the characteristics that people can pick to identify people as an out-group aren't. Once society has picked a definition of white, I can't stop myself from being under that definition. And while you're correct that it may, with time, be possible to change society's opinion on what is good or bad, in the meantime it harms a bunch of people discriminated against for things they have no control over. To those people, the characteristics society cares about are immutable.
So until society has progressed to the point that we don't give a shit what someone's race is (and don't tie it to a skin color or whatnot), and don't want to discriminate against people who are attracted to people of the same sex, we should prevent hate speech based on the immutable characteristics of race and sexual orientation.