By Ralph Novak
March 19, 1990 12:00 PM

It would be a mistake—aesthetically, morally, practically—to try to sanitize movies, get rid of gratuitous violence, sex and obscenity. For starters, try to define “gratuitous.” But even as films for young children become increasingly infected, it’s a good time to consider what there is about those of us who watch movies that encourages those who make them to think another exploding head, another glimpse of bare flesh or another curse word will generate a few more box office dollars.