What is a crime? To many, a crime is a behavior that violates the law. Laws are created to protect people from social harm, but how do we really know what constitutes a social harm?
Take for example same-sex marriage. It is unanimous among many scholars that homosexuality is natural (people are born LGBT). But yet it is considered to be an illegal "behavior" in many countries, and not too long ago it was illegal for same-sex couples to marry in all of North America because many people believed (and some still do) that homosexuality was a mental disorder.