In George Orwell's "Politics and the English Language," he lists the passive voice as part of a "catalogue of swindles and perversions" — techniques in political writing "designed to make lies sound truthful and murder respectable, and to give an appearance of solidity to pure wind."
In the active voice, the subject of the sentence takes a direct action. For example, you might say Richard Nixon made a mistake. Or a policeman hit Olsen with a tear-gas canister.
In the passive voice, the subject of the sentence is the recipient of the action. Mistakes were made. Olsen was struck in the head. Responsibility was avoided.
Telling a story of violence in the passive voice is like putting on a play where figures in shadow beat a man lying in the spotlight. The dramatic focus is on the injured party, and the attackers remain undefined.
.. passives are also devilishly useful for expressing imprecise collectivist thoughts; they squeeze the human action out of an event, taking responsibility away from real persons and casting it into thin air or onto vague collectives.
Orwell wrote that this is a vicious cycle: our language "becomes ugly and inaccurate because our thoughts are foolish, but the slovenliness of our language makes it easier for us to have foolish thoughts."