You appear to have been insensitive to the situation. When you're a student, you don't want to be the "dominant force" in the room. It was an environment where you don't really know what's going on, and you're better off listening much more than you talk.
Is it possible that this is not the only time you've been obtuse in this way, that that is why the nursing school has an issue with you?
I think your heart is in the right place. And sometimes you do everything "right" and still catch flak. But I get the feeling you charged in where it wasn't appropriate, and that maybe you do that often, just out of passion to do good things.