If you make the mistake of looking outside at that point, you're all toast
What a load of nonsense. I've posted it before but it specifically states in my Ops manual that you must follow the RA correctly AND attempt to acquire the threat visually.
So, we have
two pilots. One is flying the aircraft in response to the RA. What do you think the other one is doing, specifically?
I mean, if it's not too much bother maybe you could take a look outside or are you happy to just be a useless passenger at this point?!
Take the case, again, of Uberlingen. Maybe a turn away from the threat would have been possible if visual contact had been established. Or, if you could see that the evasive maneuver wasn't working then you could do something about it. Blindly following your TCAS isn't necessarily the best thing to do.