Reductio ad Hitlerum

A modern formal fallacy in logic:

Reductio ad Hitlerum is rationally unsound for two different reasons: As a wrong direction fallacy (a type of questionable cause), it inverts the cause–effect relationship between why a villain and an idea might be criticized; conversely, as guilt by association (a form of association fallacy), it illogically attempts to shift culpability from a villain to an idea regardless of who is espousing it and why. Specific instances of reductio ad Hitlerum are also frequently likely to suffer from the fallacy of begging the question or take the form of slippery slope arguments, which are frequently (though not always) false as well.

Which brings us to Al Gore.

Al Gore today compared the battle against climate change with the struggle against the Nazis.

[...]

Mr Gore admitted that it was difficult to persuade the public that the threat from climate change was as urgent as the threat from Nazi Germany.