I think, i.e. my thoughts on the matter but no certainty, it may be partially due to the uncertainty surrounding said bad action. There are controversies, different versions of a story, etc. Some stories arise only decades later. People have heard many different versions and may not be up-to-date. It's not always easy to keep track. So if one is very uninformed, there is quite a distance to cross into certainty on the other end of the spectrum.

An interesting question.