None of us has to be an authority to cite commonly known things about public figures. Comments like that aren't targeted against the other party in the argument.
Of course, authority is in the eyes of the beholder. But that applies to everybody on this board, including you and me. (Which means no one has to pay heed to what you or I have said thus far.)
Whether each of us has "stature" is decided by the mass and not by one or two individuals. More authoritative sources (like OED) simply get consulted more often (than, say, Mr. Prescott). Considering how little I am consulted, I can safely say that I'm no authority (compared to some other posters and mods).
Having said that, I'll leave the whole authority question for the English forums collective to decide.