Attribution

Friends have asked if a famous person allows a misattributed quote to persist, can posterity then rightly claim that the person in essence made it his own?
Misattributions abound. From Crockett, to W.C. Fields, to Mark Twain, to Shakespeare, to Christ, no independent record may exist for numerous quotes and longer works attributed to any one of them. Did those famous authors know of the misattribution? In some cases, yes, in others, no. Does a misattribution matter? In some cases yes, in others no, depending upon the circumstance.
For example, a misattributed quote not at odds with the persona of the reputed speaker brings little to no harm to posterity. On the other hand, a quote palpably at odds with a well-documented persona should not be attributed without independent documentation. Also, scholarship requires that a questionable attribution be noted.
Why? Over time, sundry wits attempt to put words into famous persons' mouths, inflating in importance some contemporary turn of phrase employed by the fabricator. Such persons constitute the harm of misattributions; poseurs of diverse intent too often fabricate plausible attributions for personal gain and deserve general condemnation.
I propose for discussion that those who claim or appear to claim a misattributed quote as their own also fail strict scholarship for very small gain. Again, scholarship should eschew plagiarism of every kind. To do less encourages the poseur who would fabricate an appeal to authority while having none.