So here is why society does not approve of homosexuality.
Society is powered by individuals, not individualism. When individuals do things for the collective, society benefits and becomes stronger. When individuals do things for themselves and act like themselves, it goes against the collective interest that society values. Herds function best when each member of the herd is seized by herd mentality.
Society would much rather have individuals sacrificing their interest in order to accommodate the greater good. Most Indians, living in the midst of overbearing social pressures, will know what I am talking about. Of course, those who urge you to attend to social needs do so only because they are reflecting social requirements and not because your not following those requirements (getting married, having children, getting a job) affects them on a personal level. It is learned behaviour.
Most individuals, no matter how individualistic they are, cater to social requirements in one way or another. They serve as capable professionals, responsible parents, social workers etc. So society forgives their individualistic excesses and tolerates them. It allows them to be artists in their spare time as long as they don’t quit their jobs or abandon their families to do so.
Also, most individuals fit somewhere or the other on society’s usefulness index. Everyone is good at fulfilling some social requirement. Even the most completely useless individuals serve the purpose of being reproductive units. A man can impregnate a woman and a woman can bear children. They have a place in society’s order of things. They provide society with more potentially useful individuals.
It is here that homosexuals disappoint society. They fail the absolute basic requirement of being socially useful. They can’t produce children. They can adopt, nurture, and bring children up as well as any heterosexual couple, but for a society which sees individuals as mere reproductive units, that doesn’t count.
Society however, is rather more tolerant towards homosexuals who are more than just homosexuals. They may be authors or politicians or actors. If they have proven their worth in the eyes of society, they become more acceptable to society. Such individuals may still face discrimination, but it will be at the hands of individuals who have assimilated social thinking on the general issue of homosexuality and not because their being homosexual somehow hurts society.
Societies are human inventions that have grown to have requirements of their own. They are not absolute structures regardless of how inviolable they may seem. While a society may see a homosexual couple as a waste of two perfectly fertile human specimens, it is only because it lacks the imagination to see individuals as more than the sum of their reproductive parts. Imagination is a human quality.