Shall I tolerate the name calling....?

My boyfriend and I genuinely love each other, and I know he would do anything for me. The one great flaw of his is that he does have the tendency to call me names when misunderstandings occur or in heated discussion, such as ****, idiot, retard.... We didn't have this problem till our relationship became a long distance relationship, so I don't know what to think or how to act. It hasn't been happening on a fairly regular basis, and he said he truly understands, and it's not going to happen again, but then it does. Yes I'm not a saint in this... I usually do something wrong by mistake. I'm a human being. I'm not perfect, such as I don't understand something that he says etc, and then it triggers this reaction. I don't know if I should even give him time to show he can change once we come back together? Or is name calling just something that shouldn't be tolerated under any cirstances? I would love to hear you opinion, and it would help me greatly. Thx!