Why do people equate racism with ignorance?

I don’t get it. Why does everyone always assume that if someone wears a racist shirt, says something racist, or actually are a racist that they are dumb, ignorant, stupid, you name it.

I am not a racist, but I don’t think that hatred makes someone ignorant. I just makes you hateful. You can be a shitty hateful person, but not be ignorant. I am sure there are plenty of intelligent people that hate others of another race for one reason or another.