I don't see how that is in any way obvious. Nor is it obvious that homosexuality is aberrant in the animal kingdom -- in fact, the available evidence argues to the contrary. In many primates, most notably bonobos, sexual release has a social bonding function quite separate from reproduction.
There's a pretty credible argument, based on animal studies, that there are selective pressures in favor of homosexuality. Incidences of homosexual behavior among animals tend to increase when overpopulation kicks in. Populations without latent homosexuality will tend to overbreed and overfeed until they all die out, while populations with that latency will find their own form of population control and survive.
The reality is that we are born with a genetic drive to heterosexuality - and only psychosocial trauma during development powerful enough to derail that drive (ie, molestation) brings about homosexuality.
TWEEEEEEEEET! Flag on the play. Using the conclusion as a premise to prove the conclusion. Ten yards and loss of down.
I'm sorry, but this is a prime example of bad science getting pushed as fact by the media. What you rarely find from the media are corrections or disclaimers. Here are two articles on the subject:
Should Humans Imitate Bonobos?
The Animal Homosexuality Myth
See my profile for more information.
(1) Animals can have diseases, deformities and dysfunctional behavior just as humans do.
(2) Animal behavior is always interesting, always worth studying and puzzling about, but is not normative for human behavior. (Otherwise we'll have to accept pervasive male dominance based on threats of bodily harm, rape as courtship behavior, killing cripples, and racism. Not to mention very poor fashion sense.)
(3) Ther are hormones, pheromones, and anatomical and physiological factors which strongly predispose to reproductive behavior. If you don't know that, you don't know much.
(4) Many intensive touching behaviors are related to dominance and bonding, but are not sexual (meaning oriented to genital arousal and release.) Those that are, e.g. those that involve male-on-male penetration and ejaculation, are exceedingly rare due to the role that female pheromones play in mammalian male arousal for a completed sexual act.
I suspect that much of the recent animal "evidence" for homosexuality --- which somehow ecaped the notice of very careful and precise zoologists who have been massively cataloguing animal behavior for lo these many centuries --- is deeply biased by cultural anthropomorphism. The same Beatrix Potter mentality that said "Oh, look, Uncle Penguin has adopted an egg" in the 19th century, would now say just as foolishly, "Oh, look, he's gay."