I think sometimes it's hard for those of us who have kids, or even those of us who want them to understand that there are some people out there who just aren't maternal or paternal, and for whom the idea of having children is just unbearable. I think though that couples should discuss the possibility of children very early into a relationship and that if one partner says that he/she does not want children, then the other needs to make their decision accordingly, and if that partner decides to stay in the relationship, then they shouldn't try to change the mind of the unwilling partner down the track. If both agree that they will not have children, then it's not really for one one who agreed to respect the wishes of the other to change their mind and think it unreasonable when the other doesn't want to back down.
I had a friend who was very adament he didn't want children. He felt so strongly about it that when he was 21 he had a vacectomy. He told all partners about it before any relationship reached any level of seriousness. He didn't have a problem with children per say, in fact he even had a relationship with a girl who had two kids from a previous relationship, but he felt that he had had such a miserable childhood, and that his parents had no maternal feelings towards him, that he didn't potentially want to bring children of his own into the world that he might feel the same way about, he didn't feel it was fair, and, fair play to the guy, he made the statement by having the snip.
I don't think we should really judge people just because they don't want the same things we do, I think it's different if there was no honesty in the first place, but if both parties were honest from the outset then the decision should be left at that.