Behavior during fights?

This might seem like a stupid question, but is it a common thing to call your partner a c*nt when you're fighting or am I highly sensitive? My ex would tell call me names and when I would tell him that it was hurtful, he would say he just gets so angry with me and that's why it happens, or else he would say "so if you're acting like a c*nt, I can't call you on it and call you a c*nt?". Am I stupid for being so upset with it?