Why do some govts prefer to pit their security forces against the citizenry?

I don’t know about you but, personally, I found the cartoon that was published in this paper some time ago interesting. A family stands in the doorway of their house late in the night, kid crouching between father’s legs and pulling at mother’s hems, all startled (I imagine) by responding to a knock on their door, only to open and be confronted by the sight of two policemen carrying a heavy object.
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Pan Butamire