To be fair, Rodney does the same thing at times.

Speaking as both a scientist and a "voodoo practitioner", I think the issue is one of clinical detachment. Looking at people as "another problem to solve" allows Carson to temporarily forget the fact that the people he is trying to help and save are his friends and extended family. Earth-based physicians don't treat their loved ones for a reason; Carson doesn't have that luxury.

This doesn't excuse the dabbling in biological warfare, but it does explain it somewhat.