Alcoholism invariably causes severe damage to the liver and other systems. It is impossible to be a responsible alcoholic if one is getting blind drunk all the time. Homosexuality does not invariably harm a person. The only way this would be analogous is if we're talking about a man who is going out having anonymous unprotected sex with other men all the time--in which case he'd be just as bad a parent as a man who goes out and has anonymous unprotected sex with other women all the time. Again, by extension of your analogy all heterosexuals are bad parents! Another false analogy.
You keep saying things are the same without proving they are the same. The only person you'd convince by these arguments is someone who agrees with you already!