Given that studies of sexuality don't 100% declare that heterosexuality is genetic and may in fact be a myriad of different pre-natal, hormonal and genetic flavours, should heterosexuality be considered a legitimate expression of human sexuality?
Heterosexuality is an absurd term, the correct term is normal sexuality. Any sexual attraction outside of man-woman attraction has no natural purpose, and is therefore biologically abnormal as is usually the bi-product of genetic problems.
Given that homosexuality is displayed in every observable animal species that re-produced through procreation, it is a natural trait. It may not be common, like left handedness, blue eyes, blond hair and porcelain skin, or being colour blind, or being deaf, or having unnattached earlobes, or fallen arches and so on. It's simply a trait. A bit like reproducing by procreation, which is on the grand scale of things a minority method of reproduction. It's also a reappearing trait. It appears in animals seperated by millions, tens of millions of years of evolution so has probably been prevailant for millions upon millions of generations.
