One would hope that the worth of one's remarks would be in their validity and not by who said them.
But when validity isn't apparent, one then looks to the speaker's qualifications. For instance, if Michael Jordan were talking about what it takes to win at basketball, I'd be strongly inclined to believe him, even if the validity of his ideas wasn't immediately apparent. Why? Because Michael Jordan has demonstrated qualifications in the subject. Quite simply, he has earned the right to be believed.
In present context, when someone says that the Lexington Avenue Line could run 40tph with changes in T/O and C/O behavior and reasonably inexpensive signal upgrades, and he backs it up with math that does not appear to be correct, it's reasonable to ask: Who is he? Has he done this before?