Question Everything? Seems a tad "conspiracy theorist"..and I don't say that lightly.
Maybe "Inquiring minds finds true knowledge"?
The idea behind that, and one of the goals for Sanctuary, is for people to start questioning what they usually take for granted, even if it may not actually lead anywhere sometimes. It's a good habit to have. But yeah, I can definitely see what you mean about it being too "conspiracy theorist" here. The only thing I would say against that is that we don't actually do any conspiracy theorist content at all.
I also like the idea behind your suggestion, but if I were to change it, I would instead like to go with our usual descriptor, "The Edge of the Civilized Internet".