Wouldn’t y’all be mad?

So my bf always asks this girl friend to go out to eat at places. I personally don’t know her but I don’t think anything wrong of it. He doesn’t know I know he asks but he gave me his Instagram password about a year ago & I never actually used it until recently that I logged in and saw the messages. I’m not sure if he remembers that I have it since I never used it. Well, I wanted to see his response if I did the same & he was telling me that I shouldn’t go because he doesn’t personally know the guy that “invited me.” I told him “well you go out with people idk too” (bc they have gone out to eat before w his friends, his friends know me tho that’s why I never thought anything of it). He denied going out w people idk, that he only hangs out with people I know, which is clearly a lie. I went on his ig again & saw this

I think it’s unfair how it’s okay for him to go out with friends, even ones I don’t know, but it’s not fine for me to do so.

Again, I don’t think anything suspicious of it but why is it that he can and I can’t