Harley's point, and mine, is whether the historical episode with the sale of indulgences shows unreliability of doctrinal development. It does not, as no previously held dogma was upset by Trent when it declared the sale of indulgencies simony.
You are correct that Jack Chick's views are shared by many Protestants. This follows from the fact that, according to Cardinal Newman, to be deep in history is to cease to be Protestant, -- it is the jack chicks that you are left with.
See post #8663. Apparently, old heresies die hard.