By the "any accident caused by something in the traffic flow hitting something jumping into that traffic flow is the fault of the former object going too fast"

By the "any accident caused by something in the traffic flow hitting something jumping into that traffic flow is the fault of the former object going too fast" logic that is wildly popular on any discussions of traffic/transportation on HN you are not at all wrong. That said, I think that sort of logic is deeply flawed and the people peddling it to be asinine. Traffic participants have an obligation to not obstruct other traffic flows (like opening your door into a bike lane, or pulling a car into traffic at insufficient speed) without appropriate care to ensure it does not require other traffic participants to take evasive maneuvers.