Well, according to the Random House Unabridged dictionary, the word ‘slur’ has both divergent senses and multiple sources. You may very well be onto something.
I thought about your question, and I think you may be right. The word ‘smear’ comes to mind as well. A person inclined to use slurs would intend to take away what makes someone else special, and instead call attention to something that is wrong with them.
That is a very good point. For example, there is a word that means ‘black’, that comes from a word in a different language that too means ‘black’, and is somehow used to hurt black people’s feelings.
If that makes sense to you then I don’t want to live in the White House.