I think people downplay this verse far too much...Although there was stirring and grumbling in the ranks, they didn't up and walk away until Jesus said this to them...I believe he exposed to them and everyone else that they not only didn't believe in him, they didn't really believe in God the Father either...
Had they believed in God, God would have revealed Jesus to them...IMHO...
I believe you’ve got it! Jesu was separating sheep and goats that day. seems we still have lots of goats.