I hope the person for the motion that male homosexuality is harmful takes a bit more of a sophisticated avenue than simply stating:
Premise (1): Homosexual sex is risky.
Premise (2): Risky behavior is immoral.
Conclusion: Therefore, homosexual sex is
immoral.
Both of these premises, after all, are false as written. Some homosexual sex is risky, as is some heterosexual sex, not to mention many nonsexual activities. Some risky behavior is immoral, but much is not. After all, driving is riskier than walking, football is riskier than chess, coal mining is riskier than accounting, and so on, but we do not conclude immorality or a public health crisis on its basis.
I also hope not to see the silly "universalizing" argument that if everyone were homosexual there'd be no society. That would be as absurd as claiming being religiously celibate is immoral because if everyone practiced it there would be no society. Or if everyone became an English teacher there'd be no society (no doctors, no agrarians, farmers, ranchers, people that transport said food to us, etc.).
Let's keep this sophisticated, guys.