Another way to make them go ballistic is to say that homosexuality is a neurosis. It’s the truth, they know it’s the truth and they know that almost anyone who thinks it over will see that it’s true. The one thing that they don’t get is that their reaction to that reveals how deeply neurotic they are.
I get them with the evolution angle. I ask them what the evolutionary benefit of fudgepacking is? Then I point out that it actually shortens their lives on average and that it is an evolutionary dead end.