Let me preface this delicate post with a fair warning: someone proposed this in a speaking class geared towards tackling difficult subjects.. and I ran with the idea a long time ago. The difficult position in this case is that we need to reexamine laws in the United States pertaining to physical relationships and restrictions therein.
The law tries to take a fuzzy subject and put it in concrete black and white terms. Obviously, there is a time in everyone's life where their naive nature can be exploited physically and sexually, and past that point they can be deemed adult enough to handle relations with healthy choices. To say everyone hits that moment the day that they turn 18 is a fucking idiotic oversimplification, but it's otherwise difficult to determine this moment in each person. Hell, for many people, this point occurs well after their first few sexual encounters.
To further complicate this issue, people cannot always control who they are attracted to. If a black guy likes white girls, he isn't in the wrong. If a male likes other males, he isn't in the wrong. If a 20 year old and an 80 year old are attracted to each other for whatever reason, society might find it weird enough for Jerry Springer but ultimately it's their life and it's a free country. But if a 20 year old dates someone three years younger, or a 26 year old is attracted to a well developed and mature 17 year old, it's criminal.
Obviously, these aren't the craziest cases of attraction that occur, but they illustrate that the current system isn't perfect or always right.
Honestly, when I was still in high school, I dated a 16 year old that really could've passed for 20, and when I was in college, I dated a 20 year old who could've passed for 16 depending on what she wore and how she had her hair done. Society has an entire genre of porn where "barely legal" petite 18 year olds dress in young attire and act sexually. Not only is this porn considered fine, it is the genre of porn that's probably the most viewed.
If the age of consent was lowered to 17 tomorrow, you think everyone would say "ew, a naked 17 year old... They're way too young." The majority of people are hypocrites about this because this issue probably doesn't affect them. If you asked me, I'd bet that there will be a major change regarding these rules in the next 50 years given how fast kids grow up these days with technology and communication happening the way that they are.