I honestly don't think e-bikes are going to be taking over the MUPs any time soon. They are expensive and most people won't see them as a substitute for a car, at least here in California. They will just see them as another toy that they may or may not want to spend disposable income on.
As a runner, I get passed by cyclists all the time on the MUP. I wave at everyone and I usually get more waves back from cyclists than other runners. You can't change what other people do, but you can change your own attitude. I almost always have a good time when I am out riding or running.