It comes across as something akin to -- "Whoops! You misused that single word! Therefore, the entirety of what you just said is invalid. I wasn't really paying attention to the message or spirit behind what you said, but I'm sure that it's invalid." If they're extra prickish about it, it also comes with the side message of "I think you're a dumb and terrible person as a result. Also, my ego is fed by finding others' small mistakes and blowing them out of proportion, so, really, I'm not worth listening to."
When I interact with such people, I try to express myself as concisely as possible; that way, there's very little to have potentially picked apart. From my standpoint, it's unfortunate that I have to do so.
I expect and welcome this behavior out of proofreaders and editors, but during brainstorming processes and expressions of general ideas, I'd rather not get completely sidetracked by pedantry.