a broken string...

Last week I attended the Pacifica quartet concert. I went specifically to see them perform the Beethoven string quartet and also to hear them play "Black Angels". I've only ever heard recordings of the latter, and was definitely eager to hear them. I must say it was a great performance. I'm not going to review it or recap everything that happened or how I felt listening, or what I think of them as musicians. Instead, I was just wondering about your feelings on audience etiquette.
During the beginning of "Black Angels" I noticed that the violist had broken a string. Now not being a string player, I definitely had to look twice, just to make sure. The quartet ended that section and the violist got up, pointed out his broken string and went to door. An announcement was made, just to keep everyone posted, and as the violist went up to open the door, he found it locked. Instead of staying quiet, the audience laughed. It was embarrasing I felt as a student here, that the stage hands weren't right back stage and ready to help. I'm sure it was very disheartening for the performer. Although, as a professional he was quick to change his string and was back on stage in no time. At this then the audience cheered.
For some reason this really bothered me. The tone of the piece was set, and it's definitely a serious piece where laughter isn't very appropriate. The quartet was able to just get back on and finish the piece with the intensity that it requires. It really was great. But shouldn't an audience be quiet during those mishaps? Maybe they felt as if they were supportive. However, it all seemed incredibly inappropriate and "lowbrow", forgive me, I had to. Perhaps it's more my problem. But it isn't fun when things like this happen, but I'm sure that they do. I would just rather the audience deal with it quietly and not laugh, and then cheer. Really? What do you think?