The complaints have nothing to do with people being upset over killing nazis in a game, they are about Bethesda seeming to be siding with SJW's/Antifa/leftists with their play on "Make America great again" saying "Make America Nazi Free again".
It's to do with the left calling everyone that disagrees with them "nazis" and Bethesda making a statement that implies they are taking sides politically, that "America is run by nazis".
Their trailer even says "not my america", another political statement that heavily suggests they side with all those that love to go around saying "not my president".
I dont think anyone cares that the game is about killing actual nazis, they care about the political implications that are being made