In the same vein as Godwin's Law (vis-a-vis the thread terminating upon inappropriate Nazi comparison, not regarding the increasing probability of such a comparison being made the longer a thread gets)
some recent genealogical
research has uncovered that in circles where referring to WWII atrocities is rare, a similar instant argument
-loss subject matter is that of the mother
of the person you are arguing with, with particular attention paid to her size, intelligence and/or sexual proclivities.
Though the first maternal invoker can be initially said to have lost the argument, if the offspring of the mother-in-question has the poor judgement to retort with a similar comment regarding the invoker's mother, both parties - and perhaps even all listeners present, if they are caught laughing or encouraging further fictional familial muck-raking - can be said to have ultimately lost.
Someone else can tell you about Godwin's Mother-in-Law.