Before Chanology, I didn't know that much about Scientology. I knew that it was a bit weird (a friend told me part of the Xenu story, LOL space cooties), that it's litigation-happy, and that it likes to use the personality/stress test to scare people into buying their shit.
After I saw the first Anonymous video, I started digging. The first website I went to was xenu.net, and expanded my search from there. I wanted to be well-informed before making the choice to go Anonymous. And holy hell, I never expected things to be as bad as they are: the rampant bullying of critics, all those deaths, the gulags, the Nazi-Holocaust-psychiatry shit.
Also, the fact that they poisoned an activist's pets (cats, IIRC) angers me to no end. Going after an innocent creature because it's owned/taken care of by someone you don't like? That says a lot, right there.
