In Native Son, how do Jan and Mary describe the Negro community when talking about trying to get them to join the communist party? What will they contribute to the party?

Jan thinks that the black community will add spirit and emotion to the Communist cause, enabling a successful revolution that overturns the rigid racial hierarchy. As Bigger drives Jan and Mary around Washington Park, he hears Jan say,

I want to work among Negroes. That's where people are needed. It seems as though they've been pushed out of everything . . . When I see what they've done to those people, it makes me so mad . . . They have so much emotion! What a people! If we could ever get them going . . . We can't have a revolution without 'em . . . They've got to be organized. They've got spirit. They'll give the Party something it needs.

When Mary chimes in, she praises "their songs and spirituals" and begins singing.
Jan and Mary both engage in a type of indirect racism themselves; while they intend to help the black community, their behavior towards Bigger and their attitude toward the black community in general is deeply problematic, as it assumes that the black community needs the help and organization of white people in order to "get going." Jan talks about the black community as if they're children: "spirited" and "emotional." His pointing out that "they have so much emotion" is his way of saying that they don't have intellect and therefore need the "white savior" to come along and rescue them. This sort of paternalizing, thoughtless approach compounds the racism that people of color already endure, and indeed, we see Bigger's discomfort as he listens to Jan and Mary talk. When Mary gets into the front seat of the car, transgressing the racial rules that Bigger is used to, Bigger "[tightens] with hate." So, though well-intentioned, Jan and Mary's description of and hopes for the black community are part of the very system they think they're fighting against.