I imagine this is an issue many people on this site can relate to (let's face it, we're Irish), so I would appreciate advice here.
We were both pretty drunk, we got talking about politics, and he got really heated.
Then the waiter screwed up an order and he got really angry. And then on the way home he started hurling abuse at the cab driver. I was shocked, he was nothing but kind and pleasant until then. It was like a totally different man.
This is a tricky situation, and unfortunately it is all too familiar.
I don't need to tell you what has to be done - you need to speak with him.
It may be that he is a recovering alcoholic who fell off the wagon, it may be that he doesn't see anything wrong with this at all, or it may be a problem he has been battling with all on his own.
Either way - don't ignore him and hope this incident goes away.
You need to know where he stands on the issue, the likelihood of it happening again, and whether or not you think he can work through it.
You also need to weigh up the work involved in your being part of his recovery.
If he has been consistently wonderful, maybe it's worth hanging on to him and working through this with him.
If you've had pain in the past over alcohol abuse, and don't want to revisit the issue, maybe you need to move on.
Only you know best.