Serge A. Storms said:
In the U.S., the only acceptable form of sex education in public school systems is total abstinence, which essentially means that if you fall somewhere between 9 and 18 in the U.S., sex will be portrayed as bad and "dirty" by your school system and awesome and without any consequences by fellow students. This makes the age of consent an utterly useless "moral stance" that politicians ride on for votes, just like being against gay marriage and for keeping "under God" on money. The age of consent is only there right now because it's easier to call everyone that has sex with a minor a pedophile than it is to attempt challenging the current system if you're trying to get elected to a public office.
EDIT: As far as actual rape goes, the courts should be capable of figuring out if the sex was consensual if the case makes it to trial (the bigger issue, of course, is getting rape cases to trial, something that the age of consent doesn't do anything to help). The age of consent simply draws an arbitrary line between what should be considered "statutory rape" and what is simply a young person fucking.