It's not vague. It says that sexual behavior is none of the government's business. Pretty clear.
Are you referring to the Constitution? What about the States' authority to enact laws that govern sexual behavior? Are of you of the opinion that isn't allowed either?
If that is your stance, what have you to say about the fact that at the time the original documents of this country were written, there were state's laws on the books (for instance) criminalizing sodomy, with quite severe punishments, and for 150 years no one considered such laws unconstitutional?