Well done @jaichai! That is some story, and I understand all too well the ability to look back with rose-colored glasses and wish for a do-over :)

My ex-brother in law, while living in Japan, and being fluent in Japanese, one day found himself in an elevator with several other Japanese businessmen. They mocked this 'white businessman' and Steve, for 30 some floors, never said a word. When they hit the main floor, he too showed them that he'd understood the entire derogatory conversation, but also being skilled in Japanese culture, he apologized for making them all look so foolish! Walked out with his 'white' head held high LOL