Ruhig Brauner!
is a German idiom which means
Calm down!
It is from Richard Wagner's opera "Ring der Nibelungen - Die Walküren", where in one scene a horse (Brauner - Bay horse) is restless and Helmwige says
„Ruhig Brauner! Brich nicht den Frieden! - Quiet, Brownie! break not the peace, now.“
Even without knowing the origin of the idiom, it was always clear to me that the origin was something that is said to a horse like in this video:
https://www.youtube.com/watch?v=Jf-0byCkZUM
My understanding of using it in online forums has always been mild ironic mockery (at most), but I noticed that it is more and more often seen as an insult. Often from people who don't know or don't understand the idiom and who think Brauner is referring to a Nazi (so calling them a Nazi or "besorgten Bürger" this way). Or maybe because no one has ever calmed down online when he was told "calm down".
So is "Ruhig Brauner!" an innocent idiom or is it an insult? Is there a difference in online/offline conversations?
EDIT: