Many people don’t quite know how to view sex from a spiritual perspective.
Sex drive, or libido, is an energy. And like all forms of energy, it has to circulate. It has to flow. If, because of religious or moral belief, one tries to be completely abstinent, and never give this libido-energy its natural outlet, pressure is going to build up and eventually find some kind of alternative outlet -- it will deviate. Energy isn't moral, it just follows its own laws. One such ''deviation'' is homosexuality, although it isn't a problematic one. If that's how someone prefers to deal with one's natural libido, that's fine. Spiritually speaking, it is not really a problem. No spiritual laws are broken by adult, consensual homosexuality -- over indulgence, attachment, and such things will be spiritual problems whether the sexuality in question is hetero or homosexual.
However, deviations that will be hugely problematic are the obvious ones. Just look at the catholic church. Deviations can cause other effects that can in various ways damage the hara (or sex) chakra, which will cause some kind of problem with sex or gender expression, or, in worse cases trap consciousness down there in such a way that a person will become a complete psychopath. Correct sex expression is important for for spiritual health and growth, and most ancient religious views on this are mostly inappropriate for modern man.