Also, I am not sure how to qualify "I just know it does" as a fallacy. The closest I'm thinking is the catchall non-sequitur, because that is an unsupported conclusion which does not follow from the premises.
Also, I am also not sure the name of the fallacy, but he is basically using Pascal's Wager here as well, because he is implying that if we DON'T just assume chiropractic works, we are essentially killing thousands of people, and so we shouldn't bother verifying it with science. Maybe appeal to emotion?