George Murchison functions as a counterpart to Beneatha in particular and also helps to show Walter's relatively liberal social views as well.
Murchison is an example of "assimilationist" attitudes, which Beneatha cannot abide and reacts against. She prefers a mode of positive, self-developed and separate identity rather than what she sees as an acquiescence to an inferior or subordinate role in a social status quo.
To Walter, Murchison represents a disdainful attitude towards people of lesser means. Walter is not equipped to parlance with George Murchison on business matters (and perhaps George is not equipped himself to discuss business), but George takes a condescending attitude toward Walter. Walter does not respect Murchison's ways, his postures, or his attitudes. He does, however, look forward to a day when he will be similarly vested in capital - or something akin to this scenario.
Instead of working his way "up the ladder" in a traditional way, Walter looks for an easier way to acquire money. This rejection of tradition is a rejection of the values that Murchison represents.
Mr. Linder is a literal representative for a group of people that want to maintain racial separation and he becomes a figurative representative for this social attitude as well. The systematic and prejudiced limitations on the Younger family is rebelled against finally and directly in the climax of the play.