A randman is nutcase, a crazy person, and doesn't notice or care if everybody around him thinks he's wacked out. The term became widely known among Florida cell phone tower builders and in various online communities where a legendary poster with the same name made himself famous. It is quite common now to describe an odd ball as a randman.
Look at that randman go on and on about the chicoms and birthers. Doesn't he realize that nobody cares?