They have been very effective at persuading generations of Latter-day Saints to question and even doubt the veracity of the foundational witnesses of the restoration.
Here's a radical new idea for them to consider. Actually, anyone who has been persuaded or even influenced by them should consider this idea.
What if Joseph Smith, Oliver Cowdery, and David Whitmer were reliable and credible witnesses?
Look at some excerpts from Oliver's eight historical letters, for example. Pick out which ones are reliable and credible and which ones aren't.
(Hint: I think they're all reliable and credible, but some of our LDS intellectuals don't.)