Blimey - I go fishing for a couple of hours and come back to this!
Frank, apologies if I upset or offended, I was talking about holding in the specific Reading incident and similar attacking movement situations when attacker has passed defender and defender grabs. In this case, the attacker is past the defender, who, beaten all ends up grabs the shirt.
Yes, there will always be physical contact in the game, and some of it is legal, some of it isn't and some of it will be missed or ignored by the referee.
In the case of corners, I do pull the players up on it if I see it happening, if more than one incident then I pick the worst if I am going to talk to the offenders, otherwise a loud and clear 'Get a room guys!' with a pointed finger is usually enough.
Once ball is in the air, then yes, it becomes a penalty or FK however, I try and judge whether it has actually impeded a player who would have got to the ball. Eg: A bit of holding at the back post when the corner is headed away before the ball reaches the near post for example. While technically a foul, it would have to be pretty obvious wrestle for me to give a penalty - usually a six of one and half dozen of the other anyway so always tough to see which way it should go.
Hope that clarifies!