Don't be that guy
Have you ever been rejected by a girl and ignored it?
Do you feel entitled to sex, just because she looked like she was interested earlier that night?
Do you think it's ok to grope a girl you like, without getting consent?
Nobody has the right to get sex, despite having bought a girl a drink or for a dinner. Or if a girl dresses up in a short skirt or said she wanted it before. Consent is always a precondition for sex.
Porn films give a jarred idea of reality when it comes to sex. Excessive use of porn can give men the idea that they are somehow more entitled to sex.
Social behaviour that needs to change
The idea of sex entitlement without consent is called rape culture and it will thrive while we excuse our friend's behaviour or deem abuse or harassment as irrelevant.
What can I do?
To respect boundaries is a fundamental element in any encounter. Look at yourself and how you talk about women. Listen to your environment and see if you find yourself taking part in a negative discussion about women without realising it. Don't take part, even if everyone else behaves like that.
Nobody can expect women to be the only propelling force to change ideas like that. You can be a part of the solution too. Take a stand against sexual violence and help your friends to take responsibility for their own behaviour.