That is a Christian attempt at using a secular argument to defend their position that homosexuality is a sin. They say that homosexuality has no precedent in nature therefore mankind can’t or shouldn’t do it.
In effect what they are saying is that we as humans need permission in the form of precedents in the lower animals before we can do something. If our actions are without precedence then they are by definition unnatural. So does this also imply that anything with precedence in nature is OK? Infanticide, cannibalism, incest?
We do many things without natural precedence. Flying in an airplane, cooking our food, wearing clothes.
But why do we need permission from nature in the first place? Didn’t “God” make us above the animals?
Homosexuality has many thousands of years of precedence in our own human species. How long does it take for something to be considered “natural”? 3000 years, 5000 years?
Homosexuality predates Christianity. Perhaps we should be looking for a religious precedence in nature first to make sure religion is natural and therefore permissible.
All arguments against homosexuality are fundamentally religious, trying to support their position that it’s a sin. But since the “sin” argument only holds sway over religious believers they looking to find secular arguments for us non believers.