I did retaliate a German couple in Munich who picked on us (my two teenagers at that time and I) that was 10 years ago. It was an isolated case that the German couple picked the wrong people that they thought they could walk all over us foreigners traveled in Munich. We were quietly waiting to get on a train while the train was pulling in to stop where the designated line that the traim would open. After the train door was open and three of us were about to step on the train and suddenly this German couple came from the side pushing us but more like shoving us away with their shopping bags and they were laughing at us that they did such ugly manner to us.
We were caught off guard that we did not expect that this kind of low class treatment would exist in the heart of Munich city where there are many tourists. After we were on the train and we happened to sit seats away from the German couple (age about in mid 20's). We began to speak in German and English loud enough to let them hear that what they did was unacceptable. We called them pig and other nasty words about racism to make them feel small. we made sure that they would have the most uncomfortable train ride they ever have. Their faces and their body languages completely changed as if they realized that they made a damn mistake to meddle with us.
They did not expect that they dealt with three people who are from New York not crossing the border to seek
asylum. They have no right to be racist to anyone like that.