The ugly truth is, not all Knights Templar are human. Some are artificially-intelligent computer programs that have been programmed to "stop war" or "safeguard mankind" and then took things either a little too literally or not literally enough. As a result, they rule mankind with an iron fist (literally). Because they aren't human, the computer tyrant sees nothing wrong with killing as many people as necessary to bring about its primary function...which is to safeguard humanity, remember? (You remember the old saying about making omelettes and breaking eggs, don't you?)
There is no arguing with one of these beings; their sense of logic has convinced them that their actions are just and fall in line with the entire purpose of their existence. Thus, anyone who opposes them must also be eliminated. Emotional appeals are useless, because generally they have no idea what emotion is or means anyway.
Occasionally, one of these computerized guardians of humanity actually proclaim themselves gods.
A Sub-Trope of both Knight Templar and A.I. Is a Crapshoot. Compare Three-Laws Compliant, especially the Zeroth Law. Can tie in with Big Brother Is Watching.
Named for a frequent Catch Phrase from the game Paranoia.