First of all, lots of mothers don't breast feed, that's why you can buy formula. Why cant two fathers provide for a kid the way a mother does? It's all relative anyway - you're assuming that the mother is actually good at it, which isn't always reality. My best friend and her sister were raised by their dad because their mother is a piece of shit and they turned out just fine. I doubt that would have been the case if their mother had been more in the picture, and I doubt that things would be different if there was a second guy around. Sure a kid might get picked on sometimes for having gay parents, but seriously, what kid in the world has NEVER gotten teased about something? I'm sure they'll learn to deal, and as kids leave that 12 year old stupid stage, they mostly stop caring about it anyway.
When it comes down to it, what matters isn't the gender of the parents. It's about the parents giving a shit, paying attention to and loving the kid, and being able to provide for them.