HOW RUDE!!!!

Diana, Holly, and I went to lunch today at Max & Ermas. Our jobs are very demanding so we do not get the luxury of not bringing work to lunch with us, but we still like to get out of the office every now and again for lunch. Well at one point I think that me, Diana, and Holly were all on our cell phones dealing with work and I have no doubt that we may have gotten a little loud. Diana had a technician on the phone that she could barely hear so she said a little louder, "Can you hear me?" Well at that very moment another restaurant patron who was seated 2 booths behind us with his girlfriend turned around and said very loudly, "YES THEY CAN HEAR YOU, I CAN HEAR YOU, AND THE WHOLE RESTAURANT CAN HEAR YOU. YOU ARE BEING VERY LOUD AND RUDE AND ARE BOTHERING EVERYONE IN THIS RESTAURANT. YOU SHOULD NOT BRING WORK TO A RESTAURANT. RESTAURANTS ARE FOR PEOPLE TO EAT AND ENJOY." I proceedeed to apologize and told him that I didn't realize that we were being too loud and the rude guy proceeded to chew out all 3 of us. He told us that we should stay at the office instead of taking work to lunch because we should not be conducting business at a restaurant. At this point I was pretty upset. The guy said some other rude things that I can't remember and Diana said, "That was very rude of you, some of us don't have the luxury of not bringing work to lunch with us"
I could not believe that this guy talked to us the way that he did. We tried to finish the rest of our meal, but at this point all 3 of us were ticked off. The guy's girlfriend was shooting Holly some pretty dirty looks whenever she would get too loud on a phone call after that. There are seriously better ways to handle a situation like that. If he would have politely told us that we are being too loud then that would have been different, but he didn't. He was really rude. I have seen lots of people with lap tops out and on cell phones when I go out to lunch. What would make someone act so rudely to perfect strangers? I wonder if one of the guys from the office had joined us for lunch if that guy would have still been rude like that? When we were getting ready to leave Diana and Holly wanted to walk the other way out of the restaurant so that we didn't pass their table, and I told them that we were all 3 going to walk right by them on our way out. We all ignored them, except for Diana who said, "Have a nice night" but the guy said something about us shouting out clients phone numbers and that people could write the number down and call our clients. First of all we didn't give out any client phone numbers while on lunch, and secondly if we did what is he going to do tell our client that we were being too loud and that we took our work to lunch?

Has anyone ever been in a situation like this or similar to this? How did you handle it? What did you say?