If that's the parent's position, then I'm not sure I agree but I can't fault them for inconsistency. In an environment where many cars are traveling faster, though, it is nonetheless irresponsible and dangerous to others to ride a bike recklessly (or otherwise be unpredictable near fast-moving traffic).
I will agree that a relatively slow-moving bicycle on a road with fast-moving cars is indeed a dangerous situation for everyone. And I would agree that having similar speed vehicles together seems safer.
However, in places with vehicles going differing speeds, I would put the onus of safety on the faster vehicles.
What was being discussed was cyclists behaving recklessly. Imagine a cyclist blowing through a red light at the bottom of a hill, where they're going ~20ish. Cross traffic with a green light isn't necessarily going to see them until the last minute even if the cross traffic is moving at an otherwise safe speed. Pay attention in a city for a while, and you'll see things like this, and it rightly pisses off both drivers and us other cyclists.
I thought we were talking about whether or not bikes can be a massive threat to cars.
I have been paying attention in a city for a while. I have seen the situation you describe, but it's rare in my experience, even with SF supposedly full of reckless fixie-riders. Dangerous driving is far more common in my experience.
Hmm, yeah, scrolling up, there was more than a little hyperbole on both sides at the root of this thread. I agree a bike is not a "a massive threat to a car"; this doesn't mean it's okay for people to ride recklessly, or that they're not endangering others when they do.
And dangerous driving is probably more common (certainly by number of instances), and it should be condemned as well.
