Should I let my boyfriend know or let it slide?

So my boyfriends cousin called me a bitch because I ignored his messages and he didn't like it after he did the same thing to me. And then went on to say that he did not mean it the way I took it because I did not take well to it. The last time I told my boyfriend that his cousin called me stupid he did not take it too well. Should I tell my boyfriend anyway knowing it would cause more drama for him and his cousin, or do I let it slide for the sake of their relationship?
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4 mo
Just to phrase it better, my apologies. My boyfriend did not take it well the last time by being upset with his cousin, not me. He took his cousin on about it and wanted to cut him off completely for calling me stupid, I'm just afraid that telling him this would be my fault if the relationship of theirs goes sour.
Should I let my boyfriend know or let it slide?
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