I don't disagree with that, but self destructive behavior, gradual/externally triggered onset, uncureability, etc are NOT defining characteristics of a "disease". Read
this list of common diseases. I dare you to find a commonality among them other than a vague, subjective sense of "they result in something bad." It's not about distinguishing homosexuality from alcoholism specifically. It's that, as someone who dearly would like this "debate" about homosexuality to no longer be a debate, I cringe any time I see someone couching their argument in a context such as "diseases" which lends itself to being used against what I see as the "right" way to go. One can never conclusively prove that homosexuality is not a disease because there is no conclusive definition of what a disease is.