The few times I've done things this rude and self-serving to others, they acted as a wake-up call that I need to adjust my attitude and keep my ego in check more often. It seems to have worked this way for you, and I'm glad you manned up and sent an apology note. Live and learn, and go forward with a bit more class.
And FWIW we live in a society that doesn't accept alcohol as an excuse for bad behavior.
As a practicing musician and professional/semi-pro entertainer, I learned long ago the virtues of how to be a good supportive audience member and patiently let others have their moment when I'm not on the stage, regardless of their skill level, especially in a distinctly non-professional amateur situation. That's my version of cool. You got your kicks by stealing someone else's thunder, embarrassing him, and ruining his night, and that's just not how it's done. You were the bully and show-off, and that's never cool or heroic, particularly for practicing musicians.
That dude might have gotten his healthy round of applause same as you, but he got robbed instead.
And I'd be willing to bet there were at least a few in that gathering who were sober and aware enough to recognize what happened and would agree with me.
Self-awareness, pretty cool stuff, ain't?
