As discussed there, pointing out that it has this feature isn't always the worst argument in the world. If you have a coherent reason why this argument is different from other moral arguments that require Godwin's Law violations for their persuasiveness, then the conversation can go forward.

EDIT: (Parent was edited while I was replying.) If "using Jews and Nazis as your example because replacing them with Venusians and Neptunians would fail to be persuasive" isn't technically "Godwin's Law", then fine, but it's still a feature that correlates with really bad moral arguments, unless there's a relevant difference here.