Bikes can and should behave much more like cars than pedestrians. They should ride on the road, not the sidewalk. They should stop at lights, and pedestrians should be able to trust them to do so. They should use lights at night. And -- of course, duh -- they should ride in the right direction on one-way streets. None of this is a question of being polite; it's the law. But in stark contrast to motorists, nearly all of whom follow nearly all the rules, most cyclists seem to treat the rules of the road as strictly optional. They're still in the human-powered mindset of pedestrians, who feel pretty much completely unconstrained by rules.
The result is decidedly suboptimal for all concerned, but mostly for the bicyclists themselves. New York needs to make a collective quantum leap, from treating bicyclists like pedestrians to treating bicyclists like motorists. And unless and until it does, bike relations will continue to be marked by hostility and mistrust.
I've been a huge fan of city cycling since I saw it working in Holland. But it just doesn't work without the infrastructure and social conventions to support it. New York clearly doesn't have it figured out yet.
The problem in Toronto seems to be somewhat different. Cyclists usually stick to the roads, but automobile drivers aren't doing enough to accommodate cyclists, and that leads to a different, even more deadly kind of hostility and mistrust. As a result, I am not terribly comfortable cycling in the city (walking and TTC seem safer and more convenient, though that may be an illusion).
Mixed use streets aren't the culprit here. They work in Holland. North American cities are the culprit. We're too individualistic to be comfortable sharing anything, even public spaces like roads.
I've been the hostile jerk myself, occasionally. I'm a runner, and on a bad day it can be easy to externalize my frustrations on the pedestrians who are "in my way." Pedestrians are oblivious to their surroundings. I'm sure I'm no better when I'm walking: engrossed in conversation or with earphones in, I must miss most of what goes on around me. And then there are the walking clichés -- the four-abreast slow-walkers, the suit coming to a sudden halt to answer a text message, the woman walking out of a door without looking or slowing, the gentleman who meanders slowly to the left so that I don't know on which side to pass him, the dogs on leashes (and some without)... it's dangerous out there for a runner, let alone a cyclist.