It's also some people's standard reaction to being insulted. And an argument can be irrefutable (1) by being right, (2) by being too vague and allusive to get a grip on, or (3) by being nonsense. Or (4) by there actually being no argument to refute. In this case, lisper hasn't made any actual argument for characterizing not having "spiritual experiences" as a kind of blindness, he's just gone ahead and done it.

(There's no shame in being colour-blind, says lisper. Quite true. There should be no shame in being unintelligent either, but most people here would be greatly displeased at being called unintelligent. There should be no shame in being ugly, but most people -- perhaps fewer here than in most venues -- would be greatly displeased at being called ugly.)