Disney definitely had a hand it in, but I think they did it because they could feel that they had to make a "one or the other" choice. And it started a long time ago with the softening of Mickey's edge. He used to be kind of an asshole. But they started to get a little image conscious as people began to question why the icon of a "family" company would have an attitude. Thus Donald was born, to offload that attitude from Mickey and turn him into the sickly sweet face of the company. That kind of got the ball rolling, and it's been going downhill ever since. To keep their family image, they felt they had to divorce themselves from anything borderline. And since families were their cash cow, they took any minor rumblings that soemthing wasn't "family friendly" pretty seriously and cut it our, rather then risk losing their base.

The "Family Friendly" filter has definately contributed to the blandification of Disney, but then I look at Pixar and see something both "Family Friendly" and "Cool," so the two aren't necessarily mutually exclusive.