Veganism

[Paleophyte]

All of the evidence suggests otherwise.

And what evidence is that? Whether moral realism is true or false is greatly disputed in philosophy.

But of course it is. They'd be out of a job if they ever ended a debate. Philosophy is the ancient and venerable art of ensuring that philosophers remain well-fed.

I'd think that the evidence would be pretty obvious.

Slavery? BTDT  and used the holy books to excuse it.
Murder? Yeah, we're down with that. Here's a rock, there's a neighbor you've got a beef with. Or if you want to seem modern, she's a witch! Burn her! We're doing it right now under the guise of 'pre-emptive strikes'.
Even your extreme example of infanticide was broken regularly and gleefully. In Ancient Carthage it was a sacred duty, and there's the father-son outing that Abraham and Isaac took up Mount Moriah. These are hardly isolated incidents. The Mayans drowned infants in their sacred cenotes. The Incas drugged them and left them to die of exposure on mountain tops. The Shang dynasty sacrificed thousands, including infants.

Rape, incest, cannibalism... There isn't a taboo that our species has developed that we don't break, frequently on a society-wide basis. Your 'moral facts' are nothing more than the latest trend. Every one of our barbarous ancestors considered themselves moral.