Is it moral to allow those less than 18 years of age on Fluther to access NSFW threads?

Seeing that 18 years of age is the de facto age of consent in the US (though not actually for about 30% of the states, or the world, for that fact), would it be moral to allow those less than that age to access NSFW threads? If you would not allow them to buy adult content from the drug store, etc. why let them have access to adult content that might be different in intent but have the opportunity to be just as graphic, would that be more moral than letting them purchase a copy of Penthouse Letters, etc., if so, why?