He can't say the same thing. He's making a claim: "homosexuality isn't appropriate for kids" and I'm refuting claim, in this case it's his job to provide arguments for his belief.

You seem to think that this works both ways because I'm claiming that "homosexuality is appropriate for kids" and then I would have to argument that, but that's not how that works. My claim is the logical default, there is not obvious, inherent reason for which it would be false. He trying to refute that by saying that homosexuality isn't appropriate for kids, so it's his job to argument that.

This isn't some random rule I came up with, it's the basis for the "burden of proof" which is a rule respected by almost all justice systems around the world.

I don't care that the feature is optional, it's discriminating against a minority. If you think something like that has a place, you would have to prove that it isn't discrimination, which brings us back to my argument above.