you know, on second thought, and after reading other responses, I may have changed my mind.
If you do challenge Bob's "authority", then just make damn sure that you have a fail-proof plan, and execute it properly. there's no use negotiating with an asshole.
now, on the other hand, you don't want to go murdering people, and the rest of the local community turns on you. this really is a fucking complicated situation.
honestly, I don't believe that there's any easy answer to this. It all depends on how well you know "Bob", and how well you can predict his moves, and whether or not the rest of the local community supports you vs. how many support Bob. As others have suggested, Bob may bring more harm to the community than good, therefore, it may be your duty to stand in his way. Like I said, complicated.
My final answer is that it's impossible to answer this scenario until you're actually in the middle of it. You should do what needs to be done depending on the situation at hand. That's really all that can be said. We all know right from wrong, so we should act accordingly when the time comes.