On the other hand, just because MKUltra existed, it doesn't follow that it was successful and that the CIA can control your mind through your television and through chemicals in the food and water supply. Yet "tinfoil" people assume the latter from the former almost universally.

Let's not abandon the premise that extraordinary claims require extraordinary proof in favor of assuming that any conspiracy theory, however outlandish, should be assumed correct simply because some conspiracies have been proven to exist in the past. People don't doubt "tinfoil hat people" because of who they are, but because they don't care to present evidence to back up their claims, or accept evidence to the contrary.