That's just it. Being a racist/bigot and saying racist/bigoted things is not illegal in the U.S. Witness the Ku Klux Klan, or the Westboro Baptist Church.
Inciting violence against specific groups is illegal, but inciting violence in general is illegal already anyways.
In Canada, where I live, your comparison would be correct (though not in the US). I happen to disagree with the way Canadian law works in this regard, too.