Appeal to authority is when you claim something is true just because an "authority" said so. MR is clearly expressing an opinion and reasons for it and it is u

Appeal to authority is when you claim something is true just because an "authority" said so. MR is clearly expressing an opinion and reasons for it and it is up to you to decide whether his experience qualifies him to make such bold claims, whether there are edge cases for exceptions and whether or not you agree or care.