He may not be capable of verbalising, or possibly, not being willing to give up drinking, he feels there's nothing to say.
My son tells me that when he's in a highly emotional state he knows if he opens his mouth he'll start crying. He also clams up verbally yet can write fluently when he needs to.
It doesn't sound like your AH has reached that point where he's willing to contemplate leaving the drinking behind. Is there any more he can say without sounding like a hypocrite?