I so agree, it is very confusing.
I also believed that "It was the alcohol talking"...then I realized when he was drunk he dumped all of his issues on me...or should I say towards me. I became his mother, his father and his sister all in one, all the pent up aggression he has towards them were taken out on me, he didn't see me, he saw them.
It has been written that drug/alcohol addicition is a symptom of a deeper rooted problem, in his case I believe that to be true.