There are people who honestly believe that? It’s not that simple, it really isn’t.
I, for example, think there are many immoral but legal things and I want it to stay that way. The law is not supposed to perfectly mirror our morality, that would be a clusterfuck, tyranny, and otherwise a really bad idea. (For example: I think not tipping in the restaurant is immoral. I, however, never ever want that to become a law. Just one example.)
In short: Just because it’s legal, doesn’t mean it’s right. Just because it’s not right, doesn’t mean it should be illegal.