During the Cuban revolution and shortly afterwards they killed or exiled like 98% of people that had positions of the Batista state or supported it or benifited from it and didnt defect, from the local to the highest level. I dont know how is that a counter example or how you reply to "we should purge reactionaries that would take action to harm us during and after the revolution" with "well thats how we got pol pot". Well yeah among a dozen other reasons i guess. But thats also how we got any project that survived more than a couple of years and was able to become stable anough and overcome the opposing forces domesticaly and worldwide to a big enough degree that it could afford the humanist apporach and turned away from any mass repression, like with Cuba