They believe that each of those pathologies are the result of insufficient acceptance by the population at large. They think that the consequences of their lifestyle choices are caused by not enough people liking them.
Basically, they are at war with reality, and think they can change it by jamming their lifestyle down everyone's throats, starting in grammar school. They actually believe this.
In a way, this is a consequence of the wide acceptance of Jacques Derrida's philosophy of Deconstructionism, which held that reality is an illusion, that everything is a construction of the mind.
Therefore we can change reality if we change our thinking. There's a strand of thought within the modern intelligencia that holds that homosexuality is normal and healthy; that it's only society that makes it dangerous.
Of course, the fact that a huge swath of our media, cultural, and educational institutions have been taken over by homosexuals may have something to do with it as well.
You think "alcoholism, drug abuse, physical abuse, depression, and suicide" are the result of "lifestyle choices?" Depression and suicide are common in young who come to puberty and find themselves burdened with a non-heterosexual orientation, at a time well before they make any "lifestyle choice."
I wonder if there's something deeper going on in that the physiology that lends itself to a homosexual orientation also lends itself to various pathologies and physical ills. I know of no studies on the matter but generally I've encountered homosexuals who also had one or more a major diseases from an early age like asthma, diabetes, mental illness, sensory problems, severe allergies, autoimmune disorders or combinations of those.
To be crass and take an evolutionary viewpoint, it's as if homosexual orientation is nature's way of weeding out defective parts from the gene pool and managing population control.