I think the idea is that the accusation of racism isn't really a concrete, well-defined concept that can be falsified: in terms of specificity, its closer to calling someone a dumbass or a butthead than it is to calling them eg a shoplifter; the former isn't legally actionable (right? Perhaps I'm wrong here), but the latter is concrete enough to be.

I'm not sure if I agree with the gp commenter, but it doesn't seem to be a particularly unreasonable opinion to hold.

I'll answer your question but I hope you answer mine: Do you think I should be able to successfully sue you for millions of dollars if you had SERIOUSLY just called me a racist? If not, we're closer in viewpoint than you want to admit.

Now to your question:

> What benefits do you think free-for-all slander and libel would give society exactly?

I DON'T favor "free-for-all" slander or libel. But to the extent that I draw the line differently from you, the benefit to society would be that society gets to debate what exactly it means to be racist and hopefully that open debate leads to something useful. I like the idea that you combat speech with more speech because I think it leads to better outcomes for all of us. I don't think it's helpful to have people live in fear of saying anything controversial.