One the one hand, it does seem kind of silly... because how could someone be "for" racism and be taken seriously? It's almost like being for illiteracy in some ways.
But the problem is that racist statements and thinking are technically legally tolerated in most, if not all, countries... as long as it doesn't result in actions that can become illegal. It's not illegal to think like -- and to largely be -- an %#$hole, afterall.
So while legally tolerated, it should be socially untolerable. Thus there is a role for applying social pressure about what society thinks should be tolerable or not -- whether that's thinking or name-calling or whatnot, on the basis of race or other physical criteria for that matter (or religious beliefs, or sexual orientation, etc.).
You cannot force racists to change. But you can shame them in their ways and thinking to reinforce behaviors that are more socially acceptable.
Racist acts are more a violation of social mores, while thinking and speaking racist violates more social norms.