Y'all are missing the point.
He's saying that Children, themselves, are never a mistake; the mistake is in having more than your fair share, i.e., breeding like rabbits, that's the mistake. Once they come, they're not a mistake but if you have "too many" and the end up in "living conditions which are at times inhumane" then you shouldn't have had so many, even though they're still not a mistake. So, the bottom line, when you put the various statements on the matter from this immanent [sic] theologian together, it's a mistake not to take precautions and have too many children but each individual child isn't a mistake but you should really know better than to have so many.
Besides, maybe we won't have to worry so much about too many children after his church adopts his new guidelines on gαy couples in October.