I’m not sure why people are getting hung up on Lukaku’s act being one of petulance, or otherwise. As far as I am aware, only Dermot Gallagher, a former referee, has used this as the reason further action should not be taken. The FA hasn’t made a distinction between petulance and violent conduct.
Law 12 of The Laws of the Game says:
“VIOLENT CONDUCT
Violent conduct is when a player uses or attempts to use excessive force or brutality against an opponent when not challenging for the ball, or against a team-mate, team official, match official, spectator or any other person, regardless of whether contact is made.
In addition, a player who, when not challenging for the ball, deliberately strikes an opponent or any other person on the head or face with the hand or arm, is guilty of violent conduct unless the force used was negligible.”
I assume the FA Review Panel deemed that Lukaku acted with negligible force, and that is why he wasn’t sanctioned.
You can’t really argue with this, as Lukaku hardly made contact with the Brighton player, and he didn’t seem to even notice the attempt from Lukaku. It will be interesting to see how the FA deal with similar incidents that don’t involve a United player though.