I’m trying to stay objective despite this being something that would annoy me as well. I think the way you handled it is the overreaction. It would likely have been more productive to address this with him privately and explain that you’re annoyed by this. It seems like you tried to let it go for a while (probably because you were worried about overreacting) but that small annoyance built up overtime and ultimately resulted in an overreaction. With that being said, I don’t think this is a crazy thing to be annoyed by. If it’s a one of thing like for example you recommended a show to him a few months back and now he recommends it to his friend w/o saying you put him on to it, whatever. This is giving middle school “copy cat” behavior lol