I get what you are saying but you cannot use that wording as the opposing side would focus on the crassness of your statement.

Smile, be friendly and call then Moms for Hitler. They will protest, be offended even. But you can back this up: “then why did they promote Hitler quotes on their frontpage? Moms for Hitler sounds fair if your group quotes the man.” There will be arguments about how this was a ‘mistake’. This is easily dismissed by finger-quoting gestures and saying “why yes, who amongst us here did not quote Hitler by accident at one point and then published it on the frontpage of the organisation, totally by <emphasise finger-quoting vigorously> ‘accident’”

You can see where this is going, it will be an utterly frustrating thing to combat this statement as it has truth in it.

So you keep calling them by that name and be sure to be polite and friendly, but just keep calling them Moms for Hitler, do not relent on this.

This vile and vicious group deserves the anguish and frustration.

What did you just achieve? Nothing really other then annoying and frustrating delusional people and make them seethe with anger and frustration.
I’ll take it…