So...I guess you are great with pedophilia, prostitution, drugs, group marriages, etc? As long as it makes people happy?
If I had to make a wild guess, without researching it of course, I don’t think the Founding Fathers, who actually wrote the Constitution, would see it your way.
I am not an advocate of changing the contract laws or the age of majority to allow adults to have sex with children.
If you're engaging in a behavior with some one else, it would not make them very happy if you forced them to do something so you could be happy. We assume children are vulnerable to adult manipulation and force and we protect them.
Regarding the other things, you tell me why they should be outlawed. In a free country you should justify your position not those who advocate freedom. Government power and restriction should be justified. Odd, that I would have to explain that on a conservative site.