What you may not appreciate is that some RC beliefs, while incredible to outsiders, nevertheless are logically inseparable from other beliefs that are shared with other Christians; once abandoned, other cracks form, and it all falls down, including parts which are widely accepted as true.
Internal consistency is a virtue to be sure, although differences in degree of internal consistency between Christian sub-sects all of whose beliefs are based on multiple irrational and/or self-contradictory premises do not mean a great deal to me personally.
RC is, as you say, the religion which "tried hardest to rationalise" all its beliefs, depending on the absolute minimum of non-rational arguments (i.e., from sacred scripture or human authority). It does this with a vocabulary which, I admit, is extremely challenging to the uninitiated. (Aristotelian/Thomistic logic and hylemorphism.) Nonetheless, within that philosophical system, it is quite consistent. It's like picking up a book on string theory -- you ain't gonna "get it" on the first pass (nor the second pass, in all likelihood.)
As a philosopher I think that it's good intellectual exercise to get to grips with bad arguments like those the Catholic church use. However there's no truth in those arguments to "get", and there are other forms of intellectual exercise which might well be more beneficial for the general LW readership.
(Sorta off-topic) I was not aware that people doubted the existence of the founder of Buddhism. If he did not exist, could a reasonable religion be attributed to him? :-)
A religion could be the most rational and consistent of religions if its sole departure from reality was a fictional founder. Christianity, for example, has a fictional founder (the Biblical Jesus never existed according to the available evidence nor anyone substantially like him) but has lots of other departures from reality as well.
FYI, this seemed decent:
http://en.wikipedia.org/wiki/Jesus_myth_theory
The preponderance of the evidence would seem to be that he really did exist.
To break up the awkward silence at the start of a recent Overcoming Bias meetup, I asked everyone present to tell their rationalist origin story - a key event or fact that played a role in their first beginning to aspire to rationality. This worked surprisingly well (and I would recommend it for future meetups).
I think I've already told enough of my own origin story on Overcoming Bias: how I was digging in my parents' yard as a kid and found a tarnished silver amulet inscribed with Bayes's Theorem, and how I wore it to bed that night and dreamed of a woman in white, holding an ancient leather-bound book called Judgment Under Uncertainty: Heuristics and Biases (eds. D. Kahneman, P. Slovic, and A. Tversky, 1982)... but there's no need to go into that again.
So, seriously... how did you originally go down that road?
Added: For some odd reason, many of the commenters here seem to have had a single experience in common - namely, at some point, encountering Overcoming Bias... But I'm especially interested in what it takes to get the transition started - crossing the first divide. This would be very valuable knowledge if it can be generalized. If that did happen at OB, please try to specify what was the crucial "Aha!" insight (down to the specific post if possible).