It has effectively prevented young people from learning about safer sex. Tragically, this has led to teenagers contracting HIV. Preventing HIV is a great deal cheaper than paying for the resulting treatment.
One of the leading causes of teenage male suicide is confusion and fear of their sexuality. By enabling sensible discussion of the issues, itself requested by teenagers, perhaps this terrible toll can be reduced.
I am a gay man raised in the 1970s in a rigorously "straight" household. All the images I saw were of heterosexuality. My images of gay men consisted of entirely negative characters, as portrayed in the media.
Did this "promote" a straight lifestyle to me? Did it change my sexuality one bit? Did it hell.