I see your point and can't disagree. Still though, a person with unwarranted expectations is just that, regardless of where they got their expectations from. It doesn't have to be a normally forceful person to suddenly decide they are going to take what they think they have been guaranteed. Most peoples brains go right out the window when sex is involved. At least that's my understanding
Edit: I'm not saying most people will behave like that. But given a big enough group I'm sure the stats would speak for themselves.