The difficulty is that there is a world of difference between a system which allows a simple, independent and anonymous ID check like you'd get at a bar, vs. an online system that inevitably stores and records your interactions.

Perhaps the best way to think of the problem is like this: Yes, kids having access to porn and NSFL content is potentially damaging to society.

However, a society where the state keeps a detailed record of everyone's personal sexual preferences is potentially even worse off.