What makes them think this is okay?

So I am curious as to why bands think it is okay to curse to their fans. The other night the girls and I went to a show and it was so much fun! But when it was one of the bands turn to play, and all they could say was "Fuck you!" personally when someone says fuck you or fuck off I dont usually enjoy it and it doesnt make me wanna listen to them. I really have no idea what makes them think its okay to disrespect their so called fans like that. I really think they are fucking stupid and they need to fuck off. Yeah? Amy knows how I feel.