My boyfriend defended another girl who was nasty to me. Is it unreasonable to be bothered by this?

Anonymous
Long story short, I was telling my boyfriend of about six months about a classmate of mine who became really nasty towards me during a uni class because I took a different position on a hypothetical, politically controversial law (this was for a mock ambassador meeting, so I was only advocating for the position I was supposed to in my assigned role). She even called me a “bitch” to someone else while I was nearby. It frustrated me so I called her a “clown” when telling the story to my boyfriend.

To my surprise, my boyfriend took me calling her a clown personally and told me that he would appreciate if I didn’t call her that. I was confused and said she was acting like one, and so he doubled down and said that I shouldn’t be calling her any names because he knows her and she’s always been “kind and professional” to him. Now, to my knowledge him and this girl have been nothing more than friendly acquaintances/classmates, so I found this really odd. I told him it was rude of him to defend her when he’s with me and she was treating me poorly. He didn’t yield, insisting that he wasn’t trying to say what she did was okay but that me calling her a name was simply an unattractive thing for me to do.

Fast forward several months later and I noticed he is still liking her cute Instagram photos (selfies and what not) and I want to tell him how this how this makes me mad but I don’t know if I’m overreacting. I know some people think the whole my enemies are your enemies thing is silly but I can’t help but feel really putt off with him not defending me, his girlfriend (and this is about the 3rd time he’s done something like this, but with other people).

Thoughts?
My boyfriend defended another girl who was nasty to me. Is it unreasonable to be bothered by this?
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