He showed an image of where they added context later. Which he rejected. Why would you think if they'd have added that to begin with this thread would have gone any different? He seemed to be saying that they were agreeing with Hitler all along. They were saying that the Left is doing what Hitler said. They were associating Hitler with the Left, not with them. They weren't advocating for that quote to be enacted. They were warning that the left HAS enacted.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.
Also, someone made the point that the context was the rest of the newsletter. I absolutely agree. If you read that, it is intuitively obvious that they could not be in agreement with the quote. But if all you did was see a quote from Hitler, and you assume without reading anything else that they were agreeing with Hitler, you're the one in the wrong here.