Serious question about NFL holding calls..

[Brian37]

In the Skins/Packers game today, I cant remember that amount of jersey grabbing with or without a flag thrown in a prior game.

I don't get it. How is it part of the rules when you are not a ball holder or a guy going after a ball holder. 

I know players always try to get away with breaking the rules and act and fake sure, but how is grabbing a jersey of a non ball holder/ runner acceptable?

I am not taking about the Redskins winning. I am talking about the flags thrown during the game AND the flags not thrown during the game.