Some guy Godwin invented this law, which is comedy & yet so true
"As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one"
Also a FAQ about the law.
I would modestly suggest that the law could be extended, to some type of logarithmic Richter scale type construct, where a Nazi label would get an extreme maximum 10 rating, but along the way other various ad hominem insults such as
gay (and all derogatory synonyms)
would be incorporated on the "Godwin scale".
Perhaps this could be a research project that someone could take up, consider this post as free consulting.