"Men and women have different but complementary genitalia and are able to advance the human race via procreational intercourse."
Congratulations. You have the very basics of biology down pat.
"Humans do not have the natural ability to procreate in a homo setting. Homosexuals cannot procreate and cannot advance the human race by themselves."
Neither can anyone who happens to be sterile. Didn't think of that, did ya Sparky?
"A homosexually inclined person is about as useful to advancing the human race as somebody who has intercourse with a fair-ground ride (does happen)."
Homosexuals supply all of the benefits to the species without further burdening it or the environment by reproducing.
A few thousand years ago this meant we had more people to hunt and gather, defend the group, rear children and so forth without having to worry that they would contribute to the population that was already struggling to sustain itself. Today we get similar benefits (and more as they pay taxes and such) without contributing to population growth so if anything homosexuality is quite useful to our species.
"Ultimately, such acts can be done, but the practitioners have deviated from what is to be considered natural."
Homosexuality occurs regularly throughout nature. It is, therefore, "natural" by any definition of the word.
"Humans only have one option if they want to survive and that is hetero. This implies homosexuality is a flaw or disease."
This is only meaningful if it were possible for everyone to become homosexual and we had no other way to procreate. Fortunately, not everyone is homosexual and even if somehow everyone did spontaneously become homosexual we now have artificial insemination technology so it wouldn't really make any difference anyway.
"Usually, effort is spent curing diseases. Homosexuality should be treated no different."
You haven't quite made that point.
