It's a very strange thing to say "as long as if my son is caring for your child you stand by your principles and decline that care" to people who have already said they wouldn't allow men to provide care to their young children in a nursery-type situation.
It's as if someone said, "I just don't think child-minders should have their dogs around young children", and you've come back with, "Well, I hope you'll stand by your principles and not let my lovely dog near your children, then!"
Erm...that's the entire point, and why you're so bothered. Because people wouldn't. Unless, of course, your son's mystery profession is very different to nursery work, and males in his profession haven't been shown to present such a markedly increased risk of sexual violence...in which case it's totally irrelevant and I don't know why you keep bringing it up?