I'm talking about a man being yanked on a cable by a train going 100+ miles per hour. That's enough to tear him apart.
What I'm saying is, there is no way a gun that small could shoot a cable that was the necessary size to hold a man (which, in the movie, it wasn't thick enough), plus be able to reel him up at such a high speed.
The Mythbusters did a test on superhero myths a few months ago, and grappling guns were one of those tested. It worked, but barely. And the grappling guns themselves were the size of crossbows.
And, as I said, if these other real-life consequences can be ignored, why can't those of permawhite?
Please, tell me, honestly, had Nolan gone with permawhite, would you be sitting here, shaking your head, going "But that would cause at least permanent blindness! Bad move, Nolan. What a shame it couldn't have been makeup."