The referenced study is one of many done over the years that have found the same thing again and again: On average, R movies don’t draw nearly as large an audience as G or PG-13 films. This is simply a cinematic fact.
Where most of these studies, including this one, err is in concluding that Hollywood studios should stop making R-rated films. What Hollywood understands that a lot of Christian or family groups don’t is that there are millions of theaters to be filled at any given moment, and a wide mix of film types is needed to maximize revenue and profit.

Think of it this way. Classic Coke sells tons more than Cherry Coke. The market for Classic Coke is much, much larger. But should Coca-Cola therefore stop selling Cherry Coke? Of course not. It’s a niche product that adds to Coca-cola’s revenues because there is a small but significant group (including me) that prefers Cherry Coke to Classic Coke. It’s the same with films.
G-rated movies do have a far larger audience, but R-rated films provide an important revenue source for studios that need to draw cash from as many different audiences as possible. Some people will never see a “Finding Nemo,” but will see a “Master and Commander” or a “Mystic River”. Others will never see a “Mystic River” but will see a “Dawn of the Dead” or a “Booty Call”. (By the way, almost every children’s film — from “Bambi” to “Stuart Little 2” to “Finding Nemo” — contains some level of violence.)

As long as there is a market for non-family fare, Hollywood will produce non-family fare. And that’s not a bad thing. Not all depictions of nudity or violence are socially destructive. The argument should not be: Hollywood must never put violence, nudity, or adult content into any movie. The argument should be: Hollywood should not market inappropriate material to minors, and it should take care to avoid gratuitous sex and violence that desensitizes people and debases the culture.