Mark Twain was actually an interesting skeptic de-bunker. His comments about faith need to be taken as they were meant, tongue in cheek.

Example, Mark Twain's caustic attack on Christian Science and its founder, Mary Baker Eddy, whom he described as "the queen of hypocrites."

From "The Toadstool Millionaires", chapter 8
Mark Twain was but one of many Americans who, during the post-Civil War expansion of the nostrum traffic, objected to a particular type of effrontery on the part of patent medicine men. Among the "blessings" of 19th-century civilization which Twain's Connecticut Yankee carried back to King Arthur's England was outdoor advertising. Knights went about sandwiched between tabards emblazoned with slogans for prophylactic toothbrushes. Other knights wielded paint-pot and stencil-plate to such good effect "that there was not a cliff or a boulder or a dead wall in England but you could read on it at a mile distance" an urgent appeal to purchase shirts "which were regarded as a perfect protection against sin."