This is the stupidest law I've ever heard. If that is indeed the case, then easily half of the teenagers in Kansas are felons and, quite likely, the lawmakers who voted for this bill! Minors with an adult is one thing, but two kids making out is a criminal offense? I don't agree with underage sex, but it happens and it isn't going to stop no matter how many laws you pass.
A way many harmful bills are passed, not just this one, is the implication that if you are not in favor of the bill then you are in favor of the activity it prohibits. That is how we end up with the obviously dicriminatory affirmative action bills and many of the other "politically correct" legislation.
If you oppose a bill banning sex between the underaged, whatever arbitrary age that may be, you are in favor of sex by the young and by extension, sex between older men and young girls. Hard to vote against that.
The same with affirmative action - if you don't favor affirmative action it is implied that you favor discriminating against blacks. Oppose hate crimes legislation and you favor hate crimes, etc.
Bad logic and intimidation by the left, usually, have put us in precarious positions as a society in some cases.