With all other things being equal, the risks of contracting a sexually transmitted disease are the same whether you're straight or gay. If you are not discerning when it comes to choosing sexual partners, and you don't take the necessary steps to ensuring your manhood remains disease-free (ie, wear a fucking condom), then you can just as easily catch genital warts or the clap from some dirty bitch, as you can catch hepatitis or HIV from having unprotected bum fun with another dude.
There's no such thing as an exclusively gay or straight STI. There are most definitely certain trends, but this doesn't even matter if you think with your head, and not with your dick.
STI's were probably a great form of population control before modern medicine went and fucked up the natural balance. Syphillis used to be deadly. Now all you have to do is go to the clinic. Same goes for basically every other disease known to man. Cancer, hemophilia/anemia, meningitis, pneumonia, the flu, asthma, broken bones, heart attacks/strokes, any number of mortal wounds, and a plethora of genetic abnormalities would have absolutely killed the fuck out of you. It was survival of the fittest. The way nature intended it. Fuck, I'd have been dead by the age of 8 if it weren't for ventolin. Killed by a couple of innocuous grass seeds.
But we've removed ourselves from the natural order. Our life expectancy has shot right up. We can and do keep every drooling retard and demented old codger alive for as long as we possibly can. If you gave birth to a flipper baby back in the day, you'd have thrown it off a cliff. But now, we have an aging and completely incapable population, that is increasing at an exponential (or logarithmic?) rate. The resources in our earth are finite. We've got fuck all left. And we need to somehow divvy up our pathetic cache of resources amongst this massively increasing collective lump of stupid meat that doesn't even appreciate it in the first place. In fact, we want more. All the time.
The only way to fix it is to kill every single person that has even a tenuous connection with medicine. When people start dying naturally again, that's when equilibrium will be re-established.
This isn't something that I want, because I will surely die if I don't have access to certain medications. But fuck, it's definitely something that I believe is right. Sorry if I've caused any offense, but I think deep down, most of us know it's the truth.