Are they? Do you have any empirical evidence that people who believe having children is great are any more inclined to complain about the bad events such as the ones in your examples than are people who do not wish to have children?
Both groups complain. You would expect it from those who don't want children for ethical reasons, as they feel they are innocent pawns in all of this, but possibly not from the pro-child camp, as they are the ones who say how great life is.
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Is this correct? I don't know a huge amount of philosophy, but from what little reading I have done, I haven't got any impression that there is any significant debate within mainstream philosophy on the question of whether the bad outweighs the good in life. In fact, I don't recall the subject even coming up in what I've read. Given that there is no objective way to measure either levels of badness or levels of goodness, it's difficult to see that any such discussion would be particularly fruitful.
There is at least one academic who has a book on this matter
http://www.amazon.com/Why-Have-Children-Ethical-Bioethics/dp/0262016982
But when I say "philosophers", I include amateurs as well, which therefore includes many of us on this thread.