[JRutledge]

They can only be ejected for Malicious Contact, not simply violent contact. If it appears the runner (or fielder) went out of their way to cause contact in a malicious way, then that is what I would look for. Players might contact each other while trying to avoid contact all together. For example a bad throw that takes a fielder in the path. This is one reason you do not ball watch and watch the runner and how they are running to the next base.

Peace