Got stuck in the movie theatres with a screaming, crying baby?

I went to the movies for the first time in ages tonight and for some reason this couple brought their baby who may have been 2 or 3 months old and she cried and whined and pooped herself all through the movie. I was pissed. movies aren't cheap and these people never took her out, changed her diaper right in the theatre and she never shut up. I turtned around and gave them some hostile stares and finally I told them to shut their baby up or I would give her a good slap across the face, well they just ignored me, obviously i never would slap a baby but it still pissed me off. i work hard for my money and it should not be wasted cause parents are too lazy to hire a sitter for their obnoxious infant. what's wrong with people these days? and was i out of line to confront them?