It's not just the arbitrary age of 16/18 that is at play here- it's the age difference. Most US states actually allow for the fact that two young people, close in age might screw without committing a crime. It's when older people start using that 'age is just a number' line that things get... sketchy. CWC is officially in that 'older' category.
(edit: I don't think CWC is a "kid diddler" either. That said, I remember how his attraction signs stuck with the minimum legal consent age for quite some time after he was beyond that age bracket and suspect that, were some teen under that age to throw herself at him, he probably wouldn't stop her. Luckily that's like saying "I might cheat on my wife if Jennifer Lawrence were to knock down my door, naked, demanding satisfaction." I don't think it's something to worry about).