Yes - definitely safer with the foster mother! And while it might not have been great with his birth mother, I have to think it would've been better than this.
I think so too, regarding adoption. I'm not at all homophobic, but I do think that the mother/baby dyad is incredibly important, and that in infants up to older toddlers at least, a mother figure should be involved in primary caregiving (whether foster mother, aunt, grandmother etc).
I'd imagine many professionals are simply overworked, uninterested, and not cynical enough - so things that should make them extra attentive instead end up just falling through the cracks. But surely concerns should've been picked up. And the foster mother being concerned - that was something that should have been paid attention to as well. That was her protective instincts going off at her, I wouldn't be surprised.
Frankly, I'm cynical, and with good reason when it comes to men - and usually my cynicism is merited. There needs to be a lot more care and attention placed on men adopting without an actively involved woman, whether they're straight, gay, or bi. The issue isn't sexuality, it's men.
As for people who refuse to believe in guilt...I can imagine a lot of people just want to put their heads in the sand, and can't stand the idea that they care about an abuser, they worked with an abuser, or that they were made complicit in the abuse without knowing. It's easier for them to just deny it.