Does it matter if a parable is based on reality?

In matters in so much as if it is based on reality then the implied moral is shown to have a grain of truth, wheras one can make up a story for any moral one wishes to impart.

If the example you gave it makes utterly no difference since nothing actually happens, whether it is a recounting of a true conversation or not it's still just words.

In the cutting above, all that happens is that a character expresses an opinion; since it is only an opinion it makes no difference who's the opinion is.In your second example, it is either an opinion (that of the author of the scrap) or a peice of anecdotal evidence (derived from the factual event).Now, neither an opinion nor an anecdote feature highly in the big tree of proof - but an anecdote is surely above an opinion.