I could agree with you that "racism" and "sexism" are often used only for signaling, and even that they are (probably) used more for that purpose in the USA than elsewhere, on average, but I don't agree that they're only used for that purpose, and I don't agree that they're a product of one moral system or that they're only used by people who hold that moral system. Some people use the words because it's easier to say one word than ten words, easier to say "racism" than to speak a whole sentence when you know the listener will understand that you are referring to the systematic differential treatment of people on the basis of skin color.