Mister Charles is a slur used to describe Vietnamese in a derogatory way. Used during the vietnam war referring to VC or Victor Charlie.
The word Mister Charles is a racial slur that has been used historically to degrade and dehumanize vietnamese. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to vietnamese. If you are unsure about whether or not it is appropriate to use the word Mister Charles, it is best to err on the side of caution and avoid using it in any situation.