One of my favorites is, ‘well there’s homosexuality in nature.’ There’s also the licking of one’s own genitals, the flinging of one’s own feces and the eating of live prey and then puking it up to feed your offspring in nature too.

In the pre-internet days, a common argument to oppose gay just-about-anything was that it wasn’t in nature, so it’s obviously some kind of human sin (as opposed to seriously-natural nature sins like murder, theft, worshiping false gods, etc.)

Then biologists pointed out that there is a lot of well-documented homosexuality of all stripes in nature.

And now it’s a straw man for these same idiots.
I’ll call this the Triple Backflip Switcheroo Fallacy.