I started to feel really open and vulnerable, cornered and diminished(...) but was a bit peeved that I felt like I had to stand there and explain myself to the inquisiton.
I hear you humble...I have been there too, and was also annoyed that I suddently felt like I had to justify myself. I agree with all the posters above- you handled the situation well. Like someone said, most of the "normal" drinkers don't even bother to observe whether you drink soda or beer. There is something true about the saying that those who are drunk like accomplices and hate sober witnesses.
And people talk anyways, but probably much less than we think. I'm prone to thinking about these scenarios too, they never lead to anything beneficial but I know from my own recent experiences that it's sometimes hard to stop them. But focusing on the positive people can help find more balance. Those who genuinely care about you will continue to stay in your life, and will be glad that you quit drinking.