My boyfriend makes fun on the basis of physical features of others. am I overreacting?

my boyfriend has an elder sister and she has a boyfriend. my boyfriend and his mother call him a 'chimpanzee'
he was telling me how his sister was on call and he called her boyfriend by this name and he got upset and cut the phone. i lost it and i told how mean it was and how it was against my values because i never made fun of anyone's physical features. he said 'u can never be my bestfriend and your behaviour is against my values'
other than all this we have a good relationship.
please help me know if I'm overreacting and i should get over it?
My boyfriend makes fun on the basis of physical features of others. am I overreacting?
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