Sometimes you just have to bicycle close to cars. Even if you take the effort to see inside parked cars (it is probably better to just watch the road), it is simply impossible to evade suddenly opening car doors if they are opened at just the wrong time.
Its a bit like saying that cyclists just have to avoid you if you would suddenly jump on the biking line.
When I'm on the freeway in the carpool lane which is flowing well, and the rest of the lanes are clogged and moving slowly, I slow down, too, as someone might suddenly pull into the carpool lane from the clogged lane. I have the right of way, but I'd prefer not to rear end anyone with at 50 mph difference in speed.
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?
The point is both parties in these situations should be mindful of the hazard. Yet only one of them is not personally at any significant risk of injury (or, in most of the US at least, prosecution) so is it terribly surprising to find that party is the one that needs the most encouragement?
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).
Sure, both should be mindful of the hazard. But as you said, since the cyclist is the one who'll get hurt, he needs to take extra care, even if it is ethically and legally the other guy's responsibility.
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.
It's also common sense as a pedestrian to look both ways when crossing a crosswalk. That doesn't mean it's not the driver's legal responsibility to stop.
Its a bit like saying that cyclists just have to avoid you if you would suddenly jump on the biking line.