The MUP I do my rides on has a 20 mph speed limit on the service roads, none on the actual 7 mile loop. The loop is wider than a normal car lane and is one way traffic. Because it's a large oval shaped loop, you don't get to see many people on it even when it's crowded. Weekends are more hazardous because there are many families that bring their children out and ride together making the two way service roads a bit more dangerous. It's not the same MUP that the OP and I were on when this incident occurred.

We get a lot of other-than-cyclists on our path (East Coast Greenway). Although we don't have any access roads to contend with like you do, we get a good amount of people (lots of moms with small kids in strollers and on-foot) whenever the weather is nice. Summer weekends, drop your speed to about 2mph, because anything can happen. I kind of enjoy the opportunity to see if I can control myself, though.
There seem to be a lot of different configurations for M.U.P's. If everybody would just take care and try to be reasonable and courteous, things would go well in all areas.

the only thing we can control is ourselves, but we can make snide remarks at the self-appointed police

the total length of mine is 25 mi, and there is are two more 13-15 mi they're working to connect them all.