Flags are symbols. Some of them have even been adopted as symbols of goodwill across the world, one such flag is the Swiss flag which is also used by the red cross organization. Then there are flags that evoke rage in some people.
Empire of Japan’s “Rising Star” flag
Normally a red brilliant sun rising on a white background, this was the flag of the Empire of Japan which colonized much of Korea, parts of China, and SouthEast Asia prior to World War II. Wearing a T-shirt with any resemblance to this flag could earn you a beating in South Korea.
The Nazi flag
This is any red flag with a black swastika drawn in a white circle in the middle. A relic from Nazi Germany, it is a darling of the right-wing extremists, but a loathsome fabric among the left-wingers. It seems to attract outrage mainly in the western world.
The Confederate Flag
A red flag with white stars crossing into the corners in blue strips, it is one of the most controversial flags you can ever fly in the United States because of its links with the slavery era and civil war.
Normally a black flag with white Arabic slogans in the middle. It has been a favorite flag to many extremist organizations in the middle east. It would be incredibly negligent on your part to wave this flag in the west.