The existence of Godwin's Law doesn't mean that nobody on the internet is allowed to mention the Holocaust, and it's not an automatic counterargument to any claim involving the Holocaust.

(Wikipedia: "The rule does not make any statement about whether any particular reference or comparison to Adolf Hitler or the Nazis might be appropriate, but only asserts that the likelihood of such a reference or comparison arising increases as the discussion progresses. It is precisely because such a comparison or reference may sometimes be appropriate, Godwin has argued that overuse of Nazi and Hitler comparisons should be avoided, because it robs the valid comparisons of their impact.")