Is there any secular reason why being gay is bad?

[kılıç_mehmet]

They can hold hands in their own houses for as long as they like. It certainly is not normal here for two males to hold hands like a man and a woman would. We do not accept such things within the limits of our public decency. You're gay? Okay. But leave your gayness at home.

You know the old saying, don't you? First they came for the Jews....

Your argument from public decency is invalid, because there can be no consensus on what constitutes public decency. If you seek to impose such things then you are no better than dictatorial majority imposing their will on the minority.

Well, I already said what constitutes public decency in many countries.
Obviously, there are some minor changes, but the minimal would hold that people do not walk around naked.
Even in the most primitive societies, there are public decency rules.
Homosexuality, too has a place within public decency.