I never said that they were the same thing, only that all Catholics are Christians. They are, Catholicism is a smaller subsection of Christianity. I used to be Catholic myself. I never had anyone tell me I wasn't Christian aside from one family in one of those fringe beliefs I was talking about. I identified as a Christian. And when needed, of the Catholic doctrine of Christianity.
There are differences between Catholicism and other groups of Christianity, of course. As I mentioned in my first post, some are big, some are small. It all depends on the two groups you are comparing. But all Catholics are Christians. It's only been some of these newer fringe groups that have started to try and exclude themselves (or other groups) out of the overall umbrella of Christianity over contradictions.
There is no Christian Christianity. Some groups have tried to label themselves as the one true Christianity, just as all religions often try to label themselves as the one true religion. But there are many different doctrines that are part of a larger Christian umbrella.
From Wikipedia...
Worldwide, the three largest groups of Christianity are the Catholic Church, the Eastern Orthodox Church, and the various denominations of Protestantism. The Roman Catholic and Eastern Orthodox patriarchates split from one another in the schism of the 11th century, and Protestantism came into existence during the Reformation of the 16th century, splitting from the Roman Catholic Church
http://en.wikipedia.org/wiki/Christianity