the Emperor's New Clothes Effect

If you, a language learner, suspect that a famous yet old work contains an error or some outdated usage, is it a good idea to reveal the source to a native speaker while asking them about it? Are they liable to blindly approving of what’s written in that work and claiming it is correct even by contemporary standards, when in fact it is wrong or unlikely in the current language?

I’ve noticed that when I ask some native speakers whether a particular dubious sentence by a respected writer is correct, they tend to claim it is so. But if instead I present a sentence similar to that writer’s in crucial respects first, they will reject it. After I reveal to them that the writer’s sentence suffers from the same problem, they will start to rationalize it. This is a manifestation of what I call the Emperor’s New Clothes Effect, and clearly detracts from the reliability of replies that learners would receive. As a learner, how would you avoid this problem?