Maggot is a slur used to describe Whites in a derogatory way. Maggots breed from filth and when the Whites came to America, they brought with them rats and diseases therefore wiping out half of the Native American population. Hence the term "maggots".
The word Maggot 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 Maggot, it is best to err on the side of caution and avoid using it in any situation.