Just because a massive organization made up of millions of people lied once

It seems you are unaware that these kinds of lies are rampant and have been documented for decades, to the point where reliable patterns have emerged:

• Michael Parenti, 1986: Inventing Reality: The Politics Of The Mass Media
• Edward Herman & Noam Chomsky, 1988: Manufacturing Consent: The Political Economy of the Mass Media.
  A five minute primer: Noam Chomsky - The 5 Filters of the Mass Media Machine

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Perhaps you’re unaware of many of the US’s atrocities, because many are hidden or distorted through the above methods. Nobody lies like the imperial core propaganda machine.