Oberon: “...why should anyone care about your particular notions of what’s healthy or natural?”
Because my “notions” about what’s healthy or natural aren’t just opinion. Some things are objective fact. Fact: the anus was not designed for intercourse. It’s physically designed to be a one way valve. Fact: homosexual sodomy has a much higher chance of passing disease. It’s an inherently unhealthy act the risks of which can be mitigated with technology but not eliminated. Fact: homosexual sex does not and cannot result in conception. It’s a natural dead end. A colony composed exclusively of homosexuals would die out in one generation. These aren’t subjective opinions. They are measurable, proven, objective facts.
There, now look at that... you've fallen back into a theistic worldview without even realizing it. A "design" requires a "Designer," which as a Christian I have no problem with at all. In fact, it's a premise I endorse. Please understand, though, that if you're going to talk about the "purpose" of the parts involved, that's the problem you're going to run into. "Purpose" requires intelligence, which requires God.
Look... you're perfectly welcome to disagree with me. I have neither need nor desire to fight with you.
What about them homo penguins and giraffes? I get this one all the time from the hom crowd on blogs. It is usually a case of male dominance or behavior in an unnatural setting like a zoo.