I thought it worth checking the origin of the phrase ‘red rag’, just to see if it meant what we think it means today
Courtesy of the OED, here are some interesting quotations
1785 Shut your potatoe trap, and give your redrag a holiday – Francis Grose in A classical of the vulgar tongue
1876 Stop that cursed red rag of yours, will you – WS Gilbert in Daniel Druce
1875 ‘What do you suppose I told you the names of those points for?’
‘Well, to to be entertaining, I thought.’
This was a red rag to a bull
Mark Twain in Atlantic Monthly