" the scientific term is homo or hetero"
Homo is a scientific term? I mean other than the broad "Homo" which includes all, i.e. Homogenous, homogenized, homo sapien? Are you attempting to hijack Homo to describe a minority of humans? And as for "gay", I think that the word became associated with homo in 1862, when "Don we now our gay apparel" appeared, meaning "Girl, your outfit is fabulous!".