That said, I've spent much of my life in cities crowded with bikes and pedestrians and the difference between a bike and a car, pretty much any kind of car, is huge.

There's the weight difference, but also the completely different posture, ability to see around you, ability to stop or even just drop your bike and jump off. Bikes are much easier to steer, as well as smaller in 'surface area' that can hit another person.

I've gone on daily commutes where I'd ride at relatively high speeds right through the tourist-infested center of Amsterdam, and while I'd not do that anymore (wiser and older), accidents were incredibly rare, despite the fact that most tourists don't understand the concept of a 'bike lane'.

In my opinion the average city biker is much more like a pedestrian than like a car driver. Obviously that doesn't mean bikers shouldn't respect the road, but putting bikers in the same category as drivers seems a bit silly to me.

(that said, high-speed cyclists are quite a bit more dangerous. but around here they usually avoid heavy-traffic areas. could be different for the US maybe)

In my opinion the key attribute isn't the size, weight, or speed, but rather simply the path being used. To me, the key distinction of pedestrians is that they have their own "road," with very different rules and specific rules to handle encounters with the other type of road. Bicycles, on the other hand, use the same road as automobiles (and usually the same lanes), with only slightly different rules than automobiles.