Brandolini's Law

The amount of energy needed to refute bullshit is an order of magnitude bigger than that needed to produce it.
Also known as the Bullshit Asymmetry Principle.
Coined in 2013 by Alberto Brandolini, an Italian programmer.
Related to the quote attributed to Noam Chomsky, "It takes a minute to tell a lie, and an hour to refute it."

Trolls rely on Brandolini's Law to tie up well-meaning people in time-consuming debunking, with a minimum of effort on their own part.