Sounds like there's not a problem with same-sex parenting, but with prejudice against same-sex parenting. I agree that can be a problem. Of course, just because kids are going to get teased is no reason for their parents not to have them, or at various times Jews, African-Americans, and various other kinds of people would have to be excluded. I don't think other people's irrational prejudice should be a reason for me not to do something. I think other people, and their children, need to learn enough courtesy to respect families that are different from their own.
OTOH, experiencing and dealing with other people's prejudice may also be beneficial. This is what the outcomes seem to say.
btw, I have 3 kids; the oldest is 22, and none of them have suffered much grief over this. It's not such a big deal as it once was.