In Chapter 7, why does Tom refer to the laison between Daisy and Gatsby in terms of "intermarriage"?

We learn early in the story that Tom is a racist. His comment “next they’ll throw everything overboard and have intermarriage between black and white” is another example of his expression of this. The context, however, is Tom’s awareness that Daisy and Gatsby have a relationship, that Gatsby is, in his terms, “making love” to his wife. The statement of interracial marriage indicates that Tom views Gatsby as an “other,” that he looks down upon him as much as he looks down upon black people. Tom’s racism speaks to his arrogance and need to make himself appear and feel better than others. His racial slur in reference to Gatsby is an insult as well as embarrassing, for the narrator then comments that Tom saw himself “standing alone on the last barrier of civilization,” with Jordan murmuring “We’re all white here.”