Privately as him why he is making these comments.
It could be that he has received information somehow and is sort of looking out for you (in a very weird sort of way) by letting you know that your drinking is becoming more public than you may have thought and thinking that he is providing "motivation" for you to change. The reason I say this is because his intentions might be honorable even though his method is clumsy (at best). Don't assume the worst. Hear him out.
I don't think it's out of line to respectfully ask him to stop doing this regardless of what he says.