Why does Dolphus Raymond pretend to drink liquor?

Mr. Dolphus Raymond is known as the town drunk, because he always carries his drink in a brown paper bag, and tends to sway a bit in his walk. Mr. Raymond is also married to a black woman and has mixed children. When running from the courthouse, Dill and Scout run into Mr. Raymond and he offers Dill a sip of his drink. Scout is wary, but Mr. Raymond promises Dill it will make him feel better. Dill takes a sip and discovers Mr. Raymond is hiding a bottle of Coca-Cola in his infamous paper bag. Scout asks why he does such a thing, and Mr. Raymond explains he feels he has to give the population some reason for his odd behavior (being friendly toward black people). Mr. Raymond believes it's easier for people to handle strangeness when they have a reason to explain it. Thus, he pretends to be a drunkard.