Oh they already made the “can’t cause pregnancy” argument. It went something like this:

Them: “Gay people can’t procreate and therefore they’re causing the downfall of civilisation and therefore they’re immoral.” Me: “Not everyone needs to procreate, gay people are a minority and they wouldn’t cause a decline in births on their own, plus we already have an overpopulation issue, and gay people can procreate in other ways like surrogacy/donation anyway. Gay people aren’t harmful for being gay and certainly aren’t immoral for simply being who they are which is fine.” Them: “Cancer is a minority, does that make it ok or not harmful?” Me: “Cancer is harmful in any numbers, gay people aren’t, and they aren’t equatable to cancer.” Them: “Gays are a cancer of humanity.”

And they basically made the “not the intended purpose argument” as an appeal to nature fallacy in claiming gays people were immoral due to supposedly being unnatural. That just turned into a ridiculous semantical argument.

Them: “Gay people are unnatural and therefore immoral.” Me: “That’s an appeal to nature fallacy. Also, not only is something not automatically immoral (or moral) just because it’s unnatural (or natural), but also homosexuality does exist in nature and is observable among other animals.” Them: “Now look who made the appeal to nature fallacy. Hypocrite.” Me: “I simply pointed out that claiming homosexuality is immoral because it’s unnatural is not only illogical but also factually incorrect because it arguably is natural. Stating something is natural isn’t an appeal to nature fallacy unless you make a normative or moral claim based on its natural status. The reason homosexuality is not immoral isn’t because it’s natural but because it’s not harmful and is a basic right of individuals to embrace their sexuality.” Them: “You said it’s natural. Therefore you’re making an appeal to nature fallacy. Now you also have to admit that the scientific method, scientific consensus about COVID-19 vaccines and evolution are an appeal to nature fallacy since science makes empirical observations about nature.” (They also used Christianity to claim homosexuality is a sin, and were anti-vax) Me: “Again, making an appeal to nature fallacy and forming normative or moral judgments based on what’s natural isn’t the same as simply observing nature and drawing likely conclusions about how it functions objectively, as in the scientific method. One is prescriptive solely based on the fact of something being natural or unnatural and makes claims about what ought to be based on what is, the other is simply descriptive about nature and what is.” Them: “Predictable that a gay shill can’t understand words.”