To explain a little further, people such as the "foot-washing Baptists" are so concerned about going to Heaven, they don't behave the way they should on earth. Such religious people don't live what they preach. They say they are religious and have no problem telling others how they should live, but in the process they forget to follow their own advice. Miss Maudie feels while living on earth, a person should show his/her humanity by being kind to others and setting a good example for others to follow. She is also referring to people who are hypocrites, those people who tell others what is right or wrong, but they don't live that way themselves.
The conversation is in Chapter 5. Miss Maudie is referring to the "foot-washing Baptists" such as Boo Radley's father. Old Mr. Radley kept Boo away from all society because, in his opinion, Boo's conduct was a disgrace to the family and, perhaps, somehow sinful. Miss Maudie suggests that "some kind of men" are so obsessed with Heaven that they never learn how to live like good, kind, human beings on earth.
Although her comments refer to the Radleys, there are implications for other Maycomb people as well. Miss Maudie is accusing Old Mr. Radley of hypocrisy - "Maycomb's usual disease."