there's no such thing as a friendzone lol
That's a little too fast! If it escalates to that? That's cool. Just don't force things like that, I'd never advocate that.
There doesn't have to be. It's usually just guys who pretend to be their friend, since they think it will increase their odds of getting the woman to change her mind after rejecting you. That's not right to do either. If you wanna be her friend, then be her friend. Accept that she doesn't see you as more. If you want more than that, don't accept the friendship. And of course, there's ways of doing that without being mean and calling her names.
Bingo.
It's based around entitlement. Oh, I deserve sex and a relationship from her just because I am nice to her.
That sort of thing isn't helped when romance in TV shows and movies push problematic to flat out unrealistic relationship BS. Look at older romantic comedies. The things they have the protagonist do to win over their love interest / obsession is pretty creepy and highly problematic at times. It ventures anywhere from really pushy to flat out stalker like. And while it would be easy to write it off and say don't pay attention to it, those sort of things have been reinforced through generations of people who have and raise their kids maybe having similair views on how to handle things etc.
Same with some love songs. Like, Baby It's Cold Outside is really f***ing weird when you realize how pushy the male singer is being when she doesn't want to stay.
The whole "nice guy" that is just being nice to get a relationship / sex is f***ed up. It's really toxic, because most of those "nice guys" are really terrible when they get rejected. Like you said, it turns into them just being mean and throwing out insults and being emotionally / verbally abusive.
And it can even be more extreme. Look at Eliot Rodger, that supposed nice guy that made a video right before he started killing people in Isla Vista because he was rejected and he thought he was owed sex and attention because he was "nice".
It's also really selfish and pretty emotionally manipulative to try to force someone into something they rejected all while carrying on a platonic relationship as a facade to get what you want.