I realize that I'm taking a very taboo stance on this issue; it's really no wonder why some have mistaken me as a pedophile or a "pedophile enabler." I ask kindly that, if you cannot handle my responses, please stop reading at this point. I've included many empty lines between here and the message body for such individuals.
And (as it's right to assume), the maturity of your average 19-year-old is noticeably different than your average 36-year-old. Why is it legal for these two to go intimate? See?
The fallacious strawman (and red herring?) argument that a teen is at a different stage of development than an adult is a bit weary and tiresome. The point of fact is that some teen boys, regardless of the rest of their brain, are in fact able to more fully understand sexual processes and make better decisions than their peers; and, for what lack of intelligence these hormonal brats are left to desire, adult men are capable of letting them (teens) go about without doing any psychological harm to them. What happens when a teen hits up a cute adult guy, and the adult lets the teen boy enjoy it without doing anything back? (I hope people don't have even a small nerve to say that it doesn't happen; they're looking at a poster who is quite the living example when he was a 14-year-old young man. *hand gestures back and forth to indicate the lovely self*) Why is the adult man still the criminal who "should have known better" and "do the right thing to refrain"? Does that even make sense? See?
I don't doubt that there is a logical rational reason as to the existence of such a line drawn. The question at hand is, why must we societal folks treat it as some be-all, end-all rigid guideline with no chance of even so much of an inch of flexibility? Other countries outside the USA practice this fluidity. "Estupro laws" in many latin-American countries, for example, ensure that, while their age of consent maybe 12-15, innocent teenagers aren't taken advantage of: even if the pubescent boy/girl has met the age of consent, any evidence of deceit, enticement or grooming when the teenager wouldn't otherwise consent still puts criminal penalty on the adult. I respond to that with higher respect than the rigid no-questions-asked 18-AoC of the USA; I think it's more integral and fair, not to mention moral.