Funnily enough, that's pretty well exactly what I did do.
I sat down and drew her a very lovely swastika, in a white circle with a red background and everything, and said in a patronising tone, "That is a swastika, symbol of the National Socialist party of Germany in the 1940s. That (pointing to flag) is a Union Flag, symbol of the United Kingdom of Great Britain and Northern Ireland. Can you tell the difference?"

Her response was "Yes but they're both used by facists", and thankfully remembered she had a lecture to go to.
( Je suis un vagabond is an unfunny, up your own arse middle class knob, Tue 26 Feb 2013, 8:51, Reply)