When fundamentalists teach people outright falsehoods under the guise of religious truth, then as these are exposed by education the people lose faith, sometimes catastrophically
One of the reasons the 'Clergy Project' was founded. To help people who actually made a career out of evangelizing come to grips with their loss of faith after reality sets in.
Your post about the individual that committed suicide reminded me of a video interview I saw that had Richard Dawkins comment on a former colleague of his. A Geologist who was apparently really bright and had the potential for great success in his field. But he was raised in a strict religious upbringing and could never reconcile the facts with his dogma. Unfortunate that a great mind was poisoned so early.