Homosexuality - whether you chalk it up to social construct or simple biological drive - is perfectly acceptable sexual behavior, as there is no mental illness, deficiency, or irrational behavior associated with the practicioner. Indeed, those individuals who are homosexual are just as autonomous and rational as any heterosexual individual. Psychologists, psychiatrists, and other mental health professionals agree that homosexuality is not an illness, a mental disorder, or an emotional problem. These conclusions were reached after many years of unbiased study.
In addition to our long history with homosexuality, we are not the only species who practices it. It is found throughout the animal kingdom, something those individuals who advocate 'natural law' as a justifiable reason for differential treatment of gays and lesbians. The debates about homosexuality, in part because they often involve public policy and legal issues, tend to be sharply polarized. Those most concerned with homosexuality, positively or negatively, are also those most engaged, with natural law theorists arguing for gays and lesbians having a reduced legal status.
I believe those who wish to treat homosexuality as negative are incorrect simply because there is no evidence that the behavior is, in fact, wrong at all from a secular perspective, and even those who argue from a biblical standpoint are at the mercy of strong, secular arguments to the contrary.