Its a bit like saying that cyclists just have to avoid you if you would suddenly jump on the biking line.
The same when biking past a row of stopped cars. Slow down, as one might open their door. It's just self-preservation.
What's the point of being in the right if you're dead?
And the difference between your scenarios is that many streets have nowhere for cyclists to ride except in the door zone, and bikes are much less visible to merging drivers/exiting pedestrians than cars, especially when those car users don't have a mindset that expects them.
Personally I almost never ride in the door zone, but that's because I'm very aggressive about taking the lane from motorists, which is a skill many cyclists are not comfortable with (and frankly our infrastructure shouldn't require them to be).
I've talked to many cyclists about this, and they invariably get angry with me about it. But like I said, what good does it to do be legally and ethically in the right when you get maimed or killed?
When I ride my bike, I treat cars like they are going to kill me. So far, it has kept me alive. Riding fast in the door zone is simply foolish, and the cyclist does have a choice - slow down!
The motorcycle community seems to have given up expecting cars to change, and they ride defensively as a result. The long time riders I've talked to all have a much more pragmatic view on this than the cyclists do. They ride on the assumption that they are invisible to cars.
Also, injuries have occurred even at low speeds.