I don't think you were wrong in any way. Sure you gave them information they didn't need or deserve to know, but they were incredibly rude to feel that they were more important than even the customer you were helping first. THEY are the ones with the problem, not you.
It's hard to deal with people like that, you did better than I would have, which is probably why I don't work directly with the public
All you can do is smile and nod your head. If they go to your boss, so be it, they'll probably be just as rude to him/her as they were to you. While the "customer is always right", that doesn't mean they should bully their way into being helped. Miserable bitter people do try to make everyone around them the same way.
Sorry you had to deal with that Virgochik, I hope you feel better!
SK