And therein resides the most important issue.
I think that people who do this kind of stuff really don't think that THEY will be the ones that get caught. Plus if it's true (which we don't know) that others covered-up for him, he probably thought he was safe. The other possibility is that if that if he did it, he's the kind of sicko who just couldn't resist the temptation that easy IM and email access to boys presented. Gambling addicts say the same thing ... easy access to online gambling is the worst tempation in the world for them. Maybe he just couldn't help but risk it all and pursue his horrible addiction.