I agree with ToughChoices. You reacted very humanely.
He was digging for an opportunity to drink (even one glass) and was looking for your approval to boot. I'm sure your mind was instantly spinning with what would have happened had you said, "sure, why not?" It's crazy-making because he put you in a position to be responsible for his choices. No wonder it triggered such intense feelings.
mle-sober said it best: "Feel free to have a drink. But if you do, I'm leaving. It's entirely your choice."
Don't forget to maintain your boundaries in all aspects of alcoholism and sobriety, silkspin. They're there to protect your feelings.