Well, of course a design implies a designer, but we’re not trying to make a case for God here. Maybe you are, but I’m only trying to point out that one can speak against the normalization and accommodation of homosexuality without using religious arguments. You just happen to hit on the word “design” to press your point. I could easily say the anus is objectively a one way valve that randomly developed that way through evolution. We can’t prove WHY it’s the way it is, but we can prove it exists and works a certain way.
I totally believe in God, but more importantly, He believes in me. My existence is dependent on Him. His is not dependent in any way on me. Nevertheless, arguments against homosexuality can be made without referencing God or religion.
True, but I actually prefer the argument from design. Because if you take the position you state, the only reason someone shouldn't put a penis in an anus is because it damages the anus. And if the owner of the anus in question doesn't particularly care, and the majority of people don't care deeply about the anuses of this small fraction of the population, then you're done.
And truly... the owners of the anuses don't care, and the rest of the world doesn't much care either, not in those terms. Apart from God and God's purpose you're just talking about so much meat. This meat will one day go the way of all flesh.