Having had more than a few close encounters with people like this (none on bikes so far thank goodness) all I can offer is that it seldom works out beneficially to anyone involved to get into a conflict of any sort with him. Even if you keep your action completely aboveboard it is bound to cause you some grief to take action against that guy. You have to decide if it's worth it or not and then decide what actions to take. I do sort of like the idea of getting several bikers to take the route and if they ALL experience the guy's actions then maybe the police will do something. Although that might just set him off more.
Can you extend the ride even MORE to another street? Or just avoid the MUP altogether and find a quiet set of streets elsewhere to ride? Would it be worth your while to ask the city to improve the narrow sidewalk section of the MUP so it is more useful and then cite your situation as respectfully as possible?