An Uber boycott is probably like a prisoner's dilemma where it can't be sustained because should it possibly work it will create a surge that will cause driver's to turn the app back on to get those pings.
There's also probably too many drivers who won't know of the boycott and won't participate.
I do think with lots of help from the press, we could create Uber slowdowns.
But you have to get the radio and tv and print press involved (and best would be to have enough of a budget to buy a couple of billboards).
An Uber slowdown would ask drivers AND the public not to use Uber at the top of the hour for ten minutes between 3 pm and 8 pm during one particular week. And explain why. And explain alternate services (Lyft, Motor, etc.) that would be available to help them get home.