I'm not going to give my friends a ride home
Why wouldn't you give you friends a ride?
I want to fool around with my girlfriend.
Did you promise them that you would give them a ride home? If so, you need to help them out even if you don't want to because you should  help them out.
Hey, I'm allowed to fool around if I want to. I'm the one leaving the party last.
You're allowed to do whatever you want, I'm just saying you should always give your friends a hand when possible.