Shards only very rarely 'make' people do anything. They pick their hosts with care, those people who are going to be inclined to use powers more or throw themselves into a given type of situation, they may nudge, or encourage more subtly, reinforcing behaviors they want with more power, more focus and utility in the power, or in damping down any drawbacks. In some cases, they may ebb and flow in terms of effectiveness, and in cases like Canary's, may ebb more for a long time, getting her to let her guard down, before a 'kill all the Japanese' chance comes up.