I [32 F] have been on and off with a [27 M] who has called me the N word and I'm confused. Why does he do that?

We dated for 3 years. He's black/mixed, for context. I'm not. But I'm also not white. He called me Bitch before. I told him not to cuss at me. And he said he does it all the time to his friends - including the women. And he does call them bitch too (jokingly). But he finally stopped after I said that was verbal abuse and I will never talk again if he does. He still says the N word a lot when he's "lecturing" me. He said words should hold no power over me. And I need to find a way to get over words since words can't actually hurt me. I need to overcome "my mental" to be a stronger person. We're now broken up, but I'm trying to make sense of why he would do that.