Belonging to a community of believers reinforces one in one's belief. If the belief is true and good, then so is the suggestibility that sustains and reinforces it.
If we weren't suggestible, we wouldn't be teachable by that highest form of teaching, indirect teaching by example. As the Danish Socrates wrote,
The essential sermon is one's own existence. (Søren Kierkegaard, Journals, #1056)