Or you could just be using this as a justification of your desire to copulate with as many strangers as possible because, you know, monogamy is not unique to the human species. So I doubt that it's a case of where human "morality" is overriding a "biological drive", unless you believe penguins and the like also have a highly developped code of ethics. In fact, the very existence of "jealousy" - an emotion that can even lead humans to kill each other - could be seen as an argument showing that monogamy is actually hard-wired into the human psyche, and perhaps those individuals who don't practice it are the unusual ones.
Either way I don't care, it's one of these argument that we will argue about 'till the cows come home but no one will actually ever be able to prove anything. Popcorn?
We want our mates to be faithful, that's what jealousy does: tries to get us to make sure our partners are carrying our genes. There are good reasons why jealousy would propagate in a non monogamous society, it probably isn't an indicator that we're monogamous by nature. Monogamy can develop in nature, and thrive, and the opposite happens too. Humans do have well documented drives however to spread their genes around, just because you don't doesn't mean a lot of people do.
Who enforces that line for the rich?
Why should anyone?
If someone makes a genetic mutation that causes them to breathe out gas that kills poor people, I would sure wish someone was drawing a line.
"It's like deja vu all over again." -- Yogi Berra