Tangent, but that's not in the movie. It was in Clarke's contributions to the script and novelization, but Clarke and Kubrick had a bitter falling out over different visions and Kubrick took out much of Clarke's stuff from the final product.
It was made explicit in the sequel movie 2010: The Year We Make Contact, but even if you don't consider that movie canon, the explanation still makes sense solely within the context of 2001, IMO.
Sounds like he acted the way HAL would have in that situation, two competing drives, remove one (kill the crew) and the task is much easier.