First, there's a really good book on this subject called Aspergers Syndrome & Alcohol. It was published in Canada but you can get it on Amazon.
Second, I have been down this road & it's common. It usually starts as a way to be accepted socially. We find it easier to make friends when we've been drinking. We are also more liked bc everyone is drinking, so they don't notice our social problems.
Third, over time, it's easy to get addicted to alcohol. When that happens, we often become mean drunks. This can last years & years, esp if we are still hanging with our drinking buddies, who are our only friends.
Fourth, I don't recommend AA bc those guys prey on autistics, esp women. They are also victim-oriented which is full of guilt & self-loathing.
Fifth, what worked for me is that someone loved me enough to tell me I had a drinking problem. I continued to drink for 2 years but it was that initial honest talk with a friend that made me eventually realize she was right & that I needed help. I went to a therapist who specialized in non-AA methods. More so, I read a book called The Tao of Sobriety and another book called The 30-Day Solution. These books are for those who do not respond to AA philosophy. Also, the book I mentioned above called Asperger's Syndrome & Alcohol which explains the Why among Aspies.
Sixth, it took me another 2 years for me to cut way down. I went from drinking daily to now I only drink on weekends. I still think about alcohol but eventually as you abstain more and more, you realized alcohol is actually wasting your life & holding you back from succeeding. It literary robs you of your energy & you become obsessed with drinking instead of working toward your life's goals.
So that's my story & I rec you have that honest talk with him...& then have him read the books & know it may take him a few years to get there, which may very well start with your candid talk. BTW interventions only work if it's THE DRINKERS IDEA - he has to want it, but it starts with a friend who loves him enough to simply be honest - so he can be honest with himself, when he's ready to see it one day.