I guess I'd be sad for those who are so worried about their wedding they freak out if anyone dances they don't like. They weren't hurting anyone and it was seriously just one dance.
Considering if the bride and groom had got pissed, they just pissed off a waitress who is just going to walk out and possibly a few other servers. Also they just lost the band since the lead singer is the mother of the waitress. So they would essentially be ending the wedding reception at that very second unless they wanted to bring out a stereo and go a little more ghetto with their seemingly fancy wedding.
"It's better to be hated for who you are than be loved for who you aren't."

Even though I liked the scene, I wouldn't have stood for them doing that at my wedding either.