Godwin's law does not invalidate argument. “[Godwin] rejected the idea that whoever invokes Godwin's Law has lost the argument, and argues that appropriate application of the rule "should function less as a conversation ender and more as a conversation starter"” - https://en.wikipedia.org/wiki/Godwin%27s_law

Note that KerrAvon invoked Godwin, not zczc. Also note that historically, some slopes have proven themselves to be actually slippery.