The idiot humans are hitting them at double the average rate; the same rate would likely apply to any slower, rule following human drivers.
I don't agree. I bet that I could get into an accident every day that wouldn't be my fault, without breaking any laws, but instead just by doing things that are unexpected by the other drivers.
A lot of people don't realize (or believe) that the biggest part of good driving is communication -- acting in a way that is predictable by other drivers, such not yielding the right-of-way when you should not, slowing unexpectedly, etc. I drive a lot, and have never had an accident, but have avoided a countless number of situations where I anticipated that a driver was about to do something stupid.