I think in this situation you did well to speak your mind and it's great that you're protecting children. I'm glad you care enough to be there for kids other than your own. I wish more would have that quality.
If it were me I would've confronted him too, but perhaps in a more calm way -- maybe with a group of parents with you and behind you, perhaps in the locker room away from the children. What's that old saying? "You can catch more flies with honey than vinegar."
Maybe ask him questions instead of assuming. Yes, he may lie, but I think you could at least get the vibe and perhaps his side of the story. It would be easy (for me at least) to see through a lie. Perhaps offer a way to find help for his attractions?
If he does have brain injury from an accident, it seems he's not getting the help he needs.
If he is a "predator" (that's such a loaded word), do you think he is likely to change his ways by means of shame and humiliation? Unlikely. It's more likely he will just find other places to be around children whose parents weren't witness to this event. But with offered help, who knows...?
The goal is to protect children in the long term AND short term, I feel.
Also, I betcha no one questions the coach, who is just as likely to molest as this guy. However, I hope we don't devolve into a society that thinks every man who enjoys working with kids is a pedophile.
Just speaking from a perspective of someone who's worked with 100s of "predators." Great job and good work for keeping kids safe!