Responses
I took it similarly: we should not had a baby if we weren't prepared or mature enough. Not like they didn't want him but they weren't ready for him. But after I read his response I then understood how it could have been interpreted. And it is still her fault she can't tell it right. Even if she didn't mean it that way she should think about her words, she just hurt him again.
I think his mom didn't mean bad with that. I took it as "We (shouldn't have been the parents) who gave birth to you." which means "You deserve better parents than me and your father who was at fault."
I actually like the mom for saying all that. At the very least, they ended things in a monotonous note.