I was in 2nd or 3rd grade when The Exorcist came out and all I remember is the grown-ups talking about it in hushed tones. I remember the teen-aged daughter of one of my mom's friends went and left in hysterics and my mom (who can be kind of a "Church Lady" at times) said, "Well, it serves her right, going to see trash like that." I think that was, more or less, the reaction of most of the adults I knew at the time.
I came across this a while back--it's a video showing actual audience reactions to the film. I guess it was a BIG thing at the time--nobody had seen anything like it before.