Godwin's Law

Godwin's law (also known as Godwin's Rule of Nazi Analogies or Godwin's Law of Nazi Analogies^[1][2]) is a humorous observation made by Mike Godwin in 1990^[2] that has become an Internet adage. It states: "As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1."^[2][3] In other words, Godwin observed that, given enough time, in any online discussion—regardless of topic or scope—someone inevitably criticizes some point made in the discussion by comparing it to beliefs held by Hitler and the Nazis.

Godwin's law is often cited in online discussions as a deterrent against the use of arguments in the widespread Reductio ad Hitlerum form.^[4] The rule does not make any statement about whether any particular reference or comparison to Adolf Hitler or the Nazis might be appropriate, but only asserts that the likelihood of such a reference or comparison arising increases as the discussion progresses. Precisely because such a comparison or reference may sometimes be appropriate, Godwin has argued that overuse of Nazi and Hitler comparisons should be avoided, because it robs the valid comparisons of their impact

SOURCE: Wikipedia