Speed, especially excessive speed or "speeding", contributes exponentially to reduced control and the frequency and severity of the consequences of 'accidents'. Speed greatly reduces ones ability to avoid and compensate for others bad driving as well, an ability essential to anyone's good driving skills.
That said, I too appreciate the challenge of remaining in control of ones anger at seeing someone mindlessly clogging up a passing lane in broad daylight when the roads are clear. That also classifies as careless, inconsiderate and irresponsible driving. But while traffic is in motion is not the time to make matters worse.