There are big differences between Catholicism and Protestantism. They have the same center, but it definitely is a large jump to convert between them. The reason the Protestant 84% is so high is because there are at least 200 different Protestant denominations in the United States. Some are similar, but many are very different. Anyone rejecting the beliefs of their parents and switching to a new Protestant denomination is not counted in this data. Yes, one of the keys of being rational is indeed constant vigilance with regards to our own biases. Once, I believed a semi-Protestant theology because I wanted it to be true, was not very knowledgeable, and didn't look too deeply into the issue. But one day I realized, as I learned more, that I had to rationally seek the truth, and choose the one belief system that I believed to be the true one. So I researched, and Catholicism always had an answer for any charge anyone tried to lay against it. I have been blessed to have never really do...