I apologize if I am repeating someone else but I have not read through every single post, for lack of time.
IMHO, alcoholism is most certainly a disease, both physical and mental, but even as a mental illness, it's physical nature involves the still, mysterious chemistry of the brain. I love the phrase, "cunning and baffling" as it is perfect in describing that mystery of science we have yet to unlock.
As to sin, I can only answer from my own Christian, (Catholic), perspective, with any depth. While drunkenness is considered a sin, similar to gluttony, unhealthy excess, alcohol itself, is not prohibited.
For something to be a sin, it must involve something which is a grave matter and which is also committed with full knowledge and deliberate consent. It's not a cop-out to say that real alcoholics, as any addicts, the idea of being able to give "deliberate consent" can be a mitigating circumstance to referring to their substance abuse as a sin. It's the same reason that people with other mental illnesses who act irrationally, (And certainly, continuing to drink for us, is irrational.), are not said to have committed a sin. That does not mean that one cannot commit sins as an alcoholic, but only that there are mitigating conditions that should discourage one from making blanket assessments of any sins involved. Give it over to God and let Him sort it out.
If anything, our alcoholism should teach us the importance to "Judge not, and ye shall not be judged: condemn not, and ye shall not be condemned: forgive, and ye shall be forgiven".
This disease has certainly humbled me before God and made me, (I hope), less judgemental and much more compassionate to the sufferings of others.