It was NOT a non-sequitur, and it is conventional practice for WRITERS to attribute quotes. Not all readers will have a background that will allow them to recognise classical sources.
As for the rest, only those who lack the ability to think clearly and assess logically will need to “revisit” an intellectual determination. How can “revisiting” based on the same criteria change a valid opinion? Unless a person has a muddled thought process, they should always arrive at the same conclusion if no factors change.