Custer is a slur used to describe Whites in a derogatory way. Used by Native Americans. I guess it means they want to see them dead like General Custer.
The word Custer is a racial slur that has been used historically to degrade and dehumanize whites. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to whites. If you are unsure about whether or not it is appropriate to use the word Custer, it is best to err on the side of caution and avoid using it in any situation.