This actually makes sense, once you understand what their problem is with communism.
You see, they have no problem with all the benefits that communism offers... What bothers them is the idea that those benefits would be given to people who haven't earned it.
Heaven, to them, is a reward. Only the pure, the righteous, the faithful get to enjoy its benefits. Heaven only works for them if they imagine that they will be able to look down and see hell.
A heaven for everyone, with no walls, no gates, no pitiful outcasts scrabbling to get in... That's no heaven at all.