Whatever unnatural acts heterosexuals decide to engage is totally besides the point. People fly, people scuba dive, people race at 200mph, all unnatural acts as well, but people who do them are not mentally disordered.
This thread is about "Is Homosexuality a Disorder?". A disorder is a thing of the MIND, and same-sex ATTRACTION is a thing of the mind. Yes, it is a disorder.
This is really simple: The most base instinct in ANY species is to procreate and perpetuate the species. Therefore, if you have an aversion to intercourse with the opposite sex, then the normal main instinct that you should have is skewed and disordered. If someone actually has an aversion to intercourse with the opposite sex, that is disordered: it is diametrically opposed to the most core instinct we have.