AIO for finding it weird that my boyfriend zoomed in on his sisters ass while we were dancing

My bf’s (25M) sister (21F) and I were dancing and singing during karaoke night and she was wearing very tiny booty shorts. We were all pretty drunk and I asked my bf to record us. We were all giggly and having a good time when we came back to look at the video. I was looking forward to watch the video, but I was barely in the video because my bf was zooming in on his sisters butt the whole time. My smile instantly dropped and I found it very weird. I didn’t want to ruin the night so I just went quiet and said I was feeling tired and wanted to go home.

My bf instantly noticed something was wrong because I didn’t want to look at him m, so I told him that I found it really weird and slimy that he recorded his sisters ass. I have three brothers and they would never do that. He told me he just wanted to point out to her that her ass was out to make fun of her and have a laugh but I just didn’t get it. Why would he zoom on it for almost the whole video when I asked him to record the both of us for the memory. He got upset with me that I would think such a thing of him but even after sobering up I found it so weird. I don’t know how to feel about and I don’t want to tell family and friends because I’m worried they’ll look at him differently. Am I overreacting ?

Tl;dr my bf recorded his sisters but and I found that weird and called him creepy. Am I overreacting ?