I have two teenage sons, they have lovely friends, the group have called out shitty behaviour by a friend but it was done in a way that says this is the end of this, let's draw a line under it and move on. This does not mean unlimited chances though.
Using TV shows we point out dodgy behaviour, eg Ross on Friends pretending to be a massage therapist to touch a half naked women, we point out good relationships, we have talked about consent and implied consent (Dh doesn't ask me if I want a hug because he knows I will want one) we have talked about one night stands and the dangers of not knowing a person well, also alcohol and the effects on behaviour.
My sons are truly great, do chores, hang up their wet towels every day, make cups of tea, we have a family dinner every day and lunch together when they are not in school etc. We talk about our day and any issues that one of them is having. They are thoughtful, caring and kind.
They are 18 and 15 now, they were never allowed to physically fight when they were younger, you couldn't hit a kid in school so you cannot hit your brother. Violence is never the answer, that goes for women slapping men too.
We have kept communication open, tried not to be horrified at some of the stuff said by others in secondary school. Every day we ask them what have they done in school, not have you had a good day, so we know what they are doing in History or Physics. Actual conversations about school. They never resorted to the one syllable grunts, totally unacceptable, they would never speak to a teacher that way. They don't get to treat us like shit just because we are their parents.
I would call it out if they spoke to Dh that way and vice-versa. Hold them accountable for their actions, work out solutions with them. Make them think for themselves and guide it rather than telling them what to do.
I was raised in a shouty and violent household. I wanted something very different for my own children.