I have no interest in joining a church, period. It doesn't matter to me whether that church spouts theistic nonsense or humanistic nonsense. I'm interested in what groups teach and what they practice, not in their rituals or atmosphere.

Certainly a rationalist group could avail themselves of techniques that make people feel good about the group. But people who join the group for the sake of those feelings, or who wouldn't join if their feelings carefully massaged, aren't rationalists. Bringing those people into the fold can only distract us from what's important and dilute the message. Syncretism requires a sacrifice of the essential nature of at least one of the two incompatible things associated.