That's an interesting perspective from the other members of the group. It sounds as if no one wanted to stand up to the guy and are all relieved now that YOU did. Has anyone taken this man aside and explained to him how Al-Anon works? Maybe that would be a good next step for one of the old-timers there.
My thought on apologies (and I have caught a lot of flak for this) is that I am often sorry for not living up to the person I would like to be by being too harsh or blunt in my delivery, or saying something a little too judgmental or critical. I may not be sorry for what I said, but how/when I said it. Often, an apology is for me, to live up to the higher self I am striving to be. This kind of thinking to certain people in my life is wrong, as those people want me to be sorry for even doing whatever it was I was doing.
An example, using this post, "I'm sorry, Mr. Dude, for calling you out on oversharing. That was wrong" versus "I apologize for handling that situation badly, and next time if I have issues with you I will handle it quietly, in private".
One acknowledges generalized wrong, while the other focuses on what, exactly, you feel "sorry" for. It may be me over-analyzing, but I think its important to clarify.
But if you don't feel sorry - then don't apologize. There is nothing fundamentally wrong with what you did.