My understanding is that dropping him is not a red card, in fact holding him is.
"The lifted player is dropped to the ground from a height with no regard to the player’s safety. A red card should be issued for this type of tackle."
http://www.rugbyrefs.com/content.php?224-Alain-Rolland-and-Sam-Warburton-s-Red-Card
@hippy started
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"The lifted player is dropped to the ground from a height with no regard to the player’s safety. A red card should be issued for this type of tackle."
http://www.rugbyrefs.com/content.php?224-Alain-Rolland-and-Sam-Warburton-s-Red-Card