First all, I'm sure someone else will say "yes, bread is bad" BUT I give it to my girls everyday also. I get old bread at a bakery and take out 4 pieces everyday. 2 for the goats and 2 for the chickens. They LOVE it!
I don't feed it all the time, but I can't think what in there is going to be that bad for the birds. I feed it when we have lots or it goes bad. Yes, I feed moldy bread to my birds and they do just fine.
We feed quite a bit of outdated bread to our chickens, cows love it too. Figure if we will eat it, the chickens can to so far as chemicals go. Main thing I can see is watch the amount you feed so you don't get their diet too out of balance.
I'm not sure if it's in the Bible or just something my Granny used to say; a man can not live on bread alone.
It's fine as a snack in the evening. By then their crop is mostly full of good stuff anyway.