I had similar arguments. In one case I got in a heated argument with him, because the "official" interpretation of a well know poem we had to analyse clearly hinged on interpreting a certain phrase in a way that was grammatically totally wrong and incongruous with the authors grasp of the language and past usage.

But no arguments would sway him, because past authorities had said otherwise, with no evidence whatsoever to support their interpretation (I could not know that my interpretation was valid either, but that was part of my point - mine at least had the advantage of not assuming the author had made a massive grammatical error right there in that one poem that he'd never made anywhere else, that just happened to totally change the literal reading of his poem).

It pretty much shattered my respect for that teacher, and strongly contributed to by burning hatred for literature analysis.