Oh yeah? Well don't get too distressed. Did I happen to mention that I'm impressed?
To the contrary, they did the right thing by admitting their ignorance in not knowing that Brownshirt refers to a group of Nazis. So the record shows that they were willing to learn. That's something.
In fact, according to a Google ngram and books search, no such term can be attested prior to the rise of the Nazis. There was no single-word brownshirt, capitalized or not, and brown shirt (two words) wasn't used as any sort of idiom referring to an oppressive military though or anything of the sort.
It also seems that a two-word form Brown Shirt also saw some use (in reference to the Nazis).