The rules since 2011 says you can't hit a defenseless receiver. He has to be able to land and protect himself.
Wrong. You can't initiate "unnecessary contact" against a defenseless player but you can contact them. Keywords underlined.
RULE 12 PLAYER CONDUCT
SECTION 2 PERSONAL FOULS
ARTICLE 9. PLAYERS IN A DEFENSELESS POSTURE. It is a foul if a player initiates unnecessary contact against a player
who is in a defenseless posture. A player who initiates contact against a defenseless opponent is responsible for avoiding an
illegal act. A standard of strict liability applies for any contact against an opponent, even if his body position is in motion, and
irrespective of any acts by him, such as ducking his head or curling up his body in anticipation of contact.
(a) Players in a defenseless posture are:
(1) A player in the act of or just after throwing a pass (passing posture).
(2) A receiver running a pass route when the defender approaches from the side or behind. If the receiver becomes a blocker
or assumes a blocking posture, he is no longer a defenseless player.
(3) A player attempting to catch a pass who has not had time to clearly become a runner. If the player is capable of avoiding
or warding off the impending contact of an opponent, he is no longer a defenseless player.
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(b) Prohibited contact against a player who is in a defenseless posture is listed below. However, these provisions do not prohibit
incidental contact by the mask or helmet in the course of a conventional tackle or block on an opponent:
(1) forcibly hitting the defenseless player’s head or neck area with the helmet, facemask, forearm, or shoulder, even if the
initial contact is lower than the player’s neck, and regardless of whether the defensive player also uses his arms to tackle
the defenseless player by encircling or grasping him;
(2) lowering the head and making forcible contact with any part of the helmet against any part of the defenseless player’s
body; or
(3) illegally launching into a defenseless opponent. It is an illegal launch if a player (i) leaves one or both feet prior to contact
to spring forward and upward into his opponent, and (ii) uses any part of his helmet to initiate forcible contact against any
part of his opponent’s body. (This does not apply to contact against a runner, unless the runner is still considered to be
a defenseless player, as defined in Article 9).