Dial is a slur used to describe Jews in a derogatory way. During WWII, the Nazis would make soap out of the fat of the burned Jews (Dial is a brand of soap). This story is said to be true, and also said to be merely war propaganda.
The word Dial is a racial slur that has been used historically to degrade and dehumanize jews. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to jews. If you are unsure about whether or not it is appropriate to use the word Dial, it is best to err on the side of caution and avoid using it in any situation.