It's not worth getting worked up about. Just be glad that people are outside being active. There are times and places on our MUP's that can be crowded. If I'm in a hurry, I would not use the MUP at those times. However, if I'm on my bike, I'm never in a hurry. If it's crowded, I just keep the speed down, and slow way down as I approach anyone.
The biggest issue for me... dogwalkers that have those leashes that stretch all the way across the trail or they let their dogs go off leash.