As much as I agree with you I have to point out the logistic of a society being so against homosexual relationships... namely that it does have an effect on producing offspring, which is a goal of all successful surviving societies. Hence why movies/tv shows always have a storyline of a man and women falling in love as that leads to marriages and for some reason marriage tend to lead to procreation... (not to mention the societal pressures for men to have sex with as many women as possible...)
Being intolerant to homosexual relationships, while wrong, is a smart move (from perspective of societies)... especially given that homosexuality isn't a black and white trait, but rather a spectrum and if you can get a good % that are on the fence or even favoring homosexuality to be in a heterosexual relationship and reproduce... the society gains a survival advantage.
Note: society can be replaced with religion and it would still make sense.
Uh, but homosexualts are a minority so procreation isn't in danger.
Also society tends to procreate a little too much, homosexuals do a lot of good by not procreating and furthermore by accepting the ******* children heterosexuals refuse to adopt into their homes and by giving them better parents than many children of heterosexuals could EVER ask for because they are 100% planned for and wanted (as opposed to some heterosexual "surprises").