Though I don't know that any of those activities are unique to same-sex couples, and the problems seemed minor and victimless.
It's... pretty close to impossible for
any act of that nature to be unique to same-sex couples (though there
are some people that like to think pegging and whatnot in a heterosexual relationship doesn't exist.
Protip: They're wrong.). Without going into details, I can think of only one thing that even comes close (well, without getting into some
really weird shit that mostly doesn't actually happen, now that I think about it... that brings the count up to two or three, maybe), and that's non-penetrative. Everything else, well, we have the most amazing peripherals these days that cover any possible gaps in capability a heterosexual couple may encounter. Which aren't exactly many. Homosexual relationships don't exactly cause the participants to sprout new limbs or unusual organs, no matter what the more insane naysayers babble.
Few decades/centuries ago, there
were some (still not exclusive to homosexual couples) medical issues, but, you know. We have easily accessible and effective lube now, and that and a few other things makes pretty much every sexual act that's not notably extreme (and some that
are) more or less as potentially harmful as any other, provided the appropriate precautions are taken.
And yeah, the other argument against it that's not
total bupkis (just mostly) is procreative. The primary problem with that, above and beyond the ones already mentioned, is that the homosexual population is simply not large enough to make or break a population's growth levels, even if methods to compensate aren't involved. You might as well have a moral scare over lifelong bachelor(ette)s or sterile couples. Which... I guess we sorta' do over the former? There's somewhat of a social stigma against that, at least in most cultures I'm aware of.
And @ Tiru: The reason those arguments are still in circulation is because some of the people advocating against homosexual relationships
lie. Constantly, irrepressibly, and heinously, to the extent their twisted fabrication of reality actually starts to gain traction. That's where the pedophilia accusations come from and how they're maintained, as well as most of the arguments out there that have been thoroughly debunked. There is an
incredible amount of straight up invented character attacks floating around against homosexuals (among others), and they're often propagated by people that are entirely aware their accusations are false, and do so pretty much entirely out of hate -- most of the rest comes from folks that are indoctrinated by those sorts, and those who just don't bother to investigate and give cursory adherence to whatever position is most vocal. It's some nasty stuff.