Godwin's Law and the Weimar Historian

A quick thought before I run out to my last day of babysitting:

Why is it that I find it mildly unfair that a corollary of Godwin's Law (yes, that's Wikipedia, and for reference purposes it's about as useful as the IMDb) is that, if one invokes Hitler or the Nazis in an argument not directly related to them, that invoker loses the argument? What if your academic frame of reference is the rise of Nazism? Am I supposed to use examples that I understand less?

On the other hand, I probably know better than anyone where Godwin got the incentive to draft said "law." You encounter it in paper marking (especially in essays that have nothing to do with the Second World War, but especially those written by first years) quite a bit. One of the first papers I marked claimed that only a Nazi would disagree with his (flawed) claims. Understandably, I took issue with that.