Turn it around on him -- make him document and support each claim and implication, with citations to primary sources. And note that Michael Moore, Air America, some random email he received from liberal moonbats, or CNN/ABC/NYT/etc. are *not* "primary sources".
In the attempt, he'll learn a lot about the unreliability of his *current* sources (due to spin, incompetence, and dishonesty), and at the very least, it'll keep him out of your hair for a while.
If you really want to drive him nuts, play it not like you're challenging him or attempting to dispute his claims, make him think you're genuinely interested in learning more and/or telling others about these "revelations", but you need more documentation before you can go forward with them.
If he manages to document some of the small details (e.g. no-bid contracts), send him back out to research whether that's an unusual arrangement in cases such as that, etc. You can keep him busy forever this way. Remember that on any item or claim, the important questions (borrowed from the excellent book, "How To Lie With Statistics") are:
1. Who says so?
2. How does he know?
3. What's missing?
4. Did somebody change the subject?
5. Does it make sense?
Hold Bob's feet to the fire until he answers those questions for *each* of his many assertions and implications.
In short, don't just reply with a length, "is not!" Walk him through how to be a critical thinker on his own material.