You know, as a parent, ideally, you will put your child first. But many parents are not much more mature than children, anyway. So they think of themselves first, and if they got pregnant accidentally, they may see the child as a trial, not a blessing. Unable to see beyond their own life and desires, they may resent the child and they may feel no compunction about making that resentment very clear.
Sure, it crosses the line. Like others, I haven’t seen anything to make me think it is happening more often than it used to, although I can imagine that happening in bad economic times. People are generally on a shorter fuse and it might be easier to lose it with your kids.
It could mess kids up pretty badly. They could grow up thinking they are mistakes and that they don’t deserve to be alive. They can end up with pretty low self esteem and a desire to correct the mistake of their birth. The thing is that, accident or not, they are alive, and anything their parents say about them is not a truth that matters. What matters is who they want to be. They can become that person whether or not their parents support them. They don’t have to get down on themselves (although it is hard not to). If they work on staying positive about themselves, they can show their parents they weren’t a mistake at all. In fact, their parents may come crawling to them on hands and knees once they become the success that eluded their parents. Success is the best revenge.