No one buys into your hyperbole statement. Must we legalize rape since we can't place cameras in every room? Must we be forced to permit pay-per-view human buffets since we can't stop every cannibalistic act?
Laws against cannibalism offend the dignity of cannibals, or so we are being told. Isn't the Libertarian position that consent alone is the arbiter of right and wrong?
As far as how can government stop gays killing and eating each other, I'd say the same way they enforce all the other laws. That is, regular investigative techniques. Letting adult gays murder each other is a little too much freedom for me. Perhaps that's my compassion getting in the way. This reminds me of the last few verses of Romans chapter 1 from The Message:
Sexually confused, they abused and defiled one another, women with women, men with men--all lust, no love. And then they paid for it, oh, how they paid for it--emptied of God and love, godless and loveless wretches.Since they didn't bother to acknowledge God, God quit bothering them and let them run loose. And then all hell broke loose: rampant evil, grabbing and grasping, vicious backstabbing.
They made life hell on earth with their envy, wanton killing, bickering, and cheating. Look at them: mean-spirited, venomous, fork-tongued God-bashers. Bullies, swaggerers, insufferable windbags!
They keep inventing new ways of wrecking lives. They ditch their parents when they get in the way. Stupid, slimy, cruel, cold-blooded. And it's not as if they don't know better. They know perfectly well they're spitting in God's face. And they don't care--worse, they hand out prizes to those who do the worst things best!