Both those scenes you described tied in with the theme of control, or lack thereof. The survivors group have no control over their lives, and were being controlled by Jessica (noble end via scummy means) and Robyn (pure manipulation.) Essentially exploring how victims of mind-rape/the ones who survive after loved ones die deal with their grief. The power was taken from them, so they took it back.
Simpson is the same way. The dude left that life to be a cop, and the power was taken from him. In retrospect, that good cop died the second Kilgrave got hold of him. Chances are he was running from a horrible situation in his former spec-ops life, and realising that he'd always be put into the role of a soldier (told what to do, no choice in the matter) he snapped and figured he'd take control of his own life. Notice how he's always trying to be the team leader in the scenarios he draws up with Jess BEFORE the pills come into play; dude has a clear issue taken orders from the get go. The pills don't create the problem, they make the existing problem worse.
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