People get excited and join in, feeling better about their lives with the assurance that they will one day be welcomed into heaven. Then the preacher calls up for people to be saved by God and join whatever church they wish, which is unheard of since most preachers just shill for their own churches. When the meeting is over, people feel refreshed and happy that even though they are oppressed and have little, God is on their side. It is ironic that people whose lives are very hard believe in God more strongly than those who are blessed with wealth or privilege, but then again the people of Stamps have to rely on something to get them through their hard days. Although Maya thinks that people should see things the way they are, in a realistic rather than a faith-tinged way, it's probably the only way people can stay optimistic in their difficult lives.
Religion also serves a perhaps less-pure purpose in black society.
Faith gives them a sense of self-righteousness, that someday they will win out over the white people and be recognized by God as better, more faithful people. However, religion in this context pacifies people to an extent that is not beneficial. It makes the people of Stamps complacent that they are being overworked and underpaid, when they should be fighting against their treatment. As such, religion seems a convenient way of keeping the black community pacified and content, like a convenient instrument of the whites. Self-righteousness is almost always a dangerous and damaging thing, though it does help the people of Stamps to bear through conditions that would be very hard to change.