Attempting to brand someone as a kook only works if there's something kooky going on. Bitcoin is exactly what it claims to be. One might find a security hole in it, but that's about all you can credibly do to discredit it.
For the layman, I submit that bitcoin sounds no less kooky than Time Cube (okay, maybe a little less kooky, at least the website styling doesn't burn your eyes and people write in grammatical sentences).
My point is that the average person doesn't understand science and much of what they believe is based on faith. In fact, that's really true for anyone, scientifically inclined or not. I didn't prove to myself all that I believe, I have sources I trust. Witness the continuing popularity of pseudoscience in popular media (astrology, natural healing, etc). People don't always believe the best sources, they have their own personal trust "network".
For many people, they will believe bitcoin works only when told so by someone they trust. Telling them to read the design paper will get you nowhere. I'm pretty sure this will happen naturally, it will just take some time.