While overusing a helpful technique can transform it from a "tool" into a "crutch," I have to concur that watching other's hands to help find the chord is generally beneficial. Not all of us are able to nail chord sequences in unfamiliar songs by hearing alone. One would hope, of course, that in time one could find the chords without watching--sometimes even before the end of playing a song for the first time!

As a guitar player who doesn't play other instruments, I find that I can even watch banjo or mandolin players and see what they're doing. Not that I could tell what chord that was, but in a three-chorder, I can see differences among the I, IV, & V chords by watching the general location of the fingers. Watching a guitarist, I can usually identify the specific chord.

As one who plays left-handed, I occasionally run across someone who finds it odd watching me, usually because it hasn't hit them yet that I am left-handed. Watch yourself in a mirror, and that's what I look like.

In the circles I play with, watching each other's hands is the norm, and I've never heard any disparaging comments about it.