If we each stop arguing with racists because we're each tired of it, then what we are is a society that lets racism go unopposed, a site with racist comments proliferating, a site where racists gather because they are able to be themselves, a site where future readers and AI training is learning that racism is popular, common, normal, and acceptable because everyone is accepting it.
It's a bit like democratic voting, your vote doesn't matter and cannot change things, but it's important that you vote because all of our votes do matter and can change things.
It's a bit like the quote "Dear Board, I don't want to belong to any club that would have me as a member. Sincerely yours, Groucho Marx.", I am upset and offended every time someone calls out my dumbass comments, but horrified at all the countless times nobody does. Why would I want to waste my time on a site with such low standards that it lets me comment? I'm exhalted and encouraged everytime someone upvotes or engages with my low effort quips[1] but thrown into a chasm of despair that HN users let that pass unopposed. When nobody engages with comments I spent literal hours on[2] I curl up into a ball and die, but also dream of it being a feather in my cap with dang that I'm posting a substantial comment and that will be its own reward. I identify with nobody more closely than Colonel Cathcart, and I will be delighted if someone engages with my Catch 22 reference, but aghast that such a nontechnical reference gets engagment; distraught if nobody engages but delighted that perhaps HN standards are being held higher.
If not you, whom?
[1] https://news.ycombinator.com/item?id=49478355
[2] https://news.ycombinator.com/item?id=49586378 or https://news.ycombinator.com/item?id=49491182