I'm going to see a concert with sexist lyrics against my gf's wishes.
So, you want to go to the concert, and you want to ignore your girlfriend's request?
Yes, but if my girlfriend liked the lyrics during the concert, she could join me.
I'm sure you really want to go to the concert, but you should rethink going if it will upset your girlfriend. Maybe plan a date night with her instead.
Why should I not do what I want because it would bother someone else even though it doesn't affect them?
It would be one thing if you were forcing her to go. But I don't see why she's allowed to ban you from going.