From the Anchor Hold has a passionate post on 'what is a Catholic'. Having been a cafeteria Catholic myself, I'm all for inclusivity. Would I have come back to the Church sooner if I felt I was out of it? I don't know. When I was a cafeterian, I felt a sort of limbo. I felt neither fully saved, nor fully damned, neither fully Catholic, nor fully not. Why? Because of mixed signals. I liked views some had that Jesus preached only against hypocrisy. "Let he who is without sin cast the first stone." But I also had that old Catholic grade school talking back at me. I took comfort in the examples around me, Catholics who were going wild, and I could justify my behavior that way. Sin, as preached in the bible or in the "old days", had possibly become redefined or outmoded. If the Church had stated its creed more clearly or preached more damningly perhaps I would've despaired and grown bolder in my sin. Or reformed.
Where the self-definition of Catholic begins to break down is when you publically espouse beliefs contrary to Catholic doctrine ala a Francis Kissling of "Catholics for Choice" and a Garry Wills. And for Catholic politicans who sanguinely vote pro-choice while trumpeting their Catholic roots.
But they say that the sin you haven't committed is the one you think is the worst. There but for the grace of God, go I. Their addiction to the wielding of power is equivalent, or in many cases more powerful, then the poor sinner who feeds his addiction with sex, drugs or rock 'n roll. Ex-communication rightly lies in the hands of bishops. We have to "dance with the one what brung you" and the apostolic line of bishops have brought us to this place, this faith.