Since simply adding a little context would have stopped this mess, in today's environment, yes it was an unforced error. You have to be cognizant of how things can be twisted, and work to not make it easy.Again, I’ll point to how differences in worldviews impact’s interpretation. People with a right leaning worldview understand the quote to be a warning and an accusation against the left, not an endorsement, because they all understand the problem the same way.
People with a left wing worldview see it as an endorsement, because to them, the only reason right wing people would quote Hitler, is because they agree with him.
About that worldview, the problem is that you guys have been telling yourselves in bad faith for so long that the right wing is next to Nazism, that you now believe it. So to you, (collectively "you") the most natural interpretation, the easy one, isn't ever the charitable one. And by charitable, I mean the most rational one.
Okay, so is it really an unforced error for a right wing parent's advocacy group to use a Hitler quote to warn people about what the left wing clown people are doing? In other words, did it even occur to you that they're identifying who is really on Hitler's side here?
Is it an unforced error? An unforced error to me is 1) to do something that undermines your potential for success, and 2) in such a way that even the least charitable interpretation of it is also the correct one.
Should this group have anticipated all the ways opponents might apply the least charitable AND incorrect interpretation? That list is infinite. Hitler quote or no, you guys already think they're Nazis anyway. So any mention of Hitler, no matter the context, is all clown world's eager to be clutched pearls need.