But, on the other hand, you should not be taking unnecessary risks — and leaving your kids with strangers (even if they look frum) is a definite risk.
For goodness’ sake, he had to go to the bathroom, and asked a frum guy to watch his kids for a minute! The chances of that particular person being a psycho are infinitesimal, and (I agree with Droid that) you can’t live your life paranoid.
Driving is a risk, as is crossing the street. should we avoid those?