‘Reductio ad Hitlarium’ is a logical fallacy and translated into English, it means “X is bad since Hitler liked X”. Interestingly, this very comparison was used for long to vilify atheists and even vegetarians at one point in time.
In close relation to the above fallacy, Mark Godwin had stated in 1990 that when a Usenet discussion becomes longer, the probability of a comparison to either Hitler or the Nazis tends to approach.
Today, Godwin’s law is the most famous internet laws that applies to chatrooms, forum threads and other forms of online discussions. At its core, Godwin’s law describes a total loss of proportion and therefore seriousness of a discussion. Cases in point, any time a new Labor law or the rise of a politician is discussed, the inclination to label it Nazi or Hitleresque by some person or group is ever so clear.
In many online situations, Godwin’s Law is used in a prescriptive manner. For instance, if in a certain forum discussion, Nazis are mentioned, then a user may invoke Godwin’s Law thereby leading admins to end that thread for fear of backlash.
However, there are situations when Godwin’s Law has been used deliberately to win arguments. In such cases, the law doesn’t apply and in fact the other party can invoke what’s called a ‘Quirk’s Exception”.