I heard one criticism for Season 6 was the seemingly-useless Walid arc. He's sent to work undercover in a prison to see if some of the imprisoned Muslims are affiliated with Fayed, but turns out they're just spectators so it was all for nothing.
Outwardly, this seems like a waste of viewers' time and that it has nothing useful to contribute to the plot, but I think it does have one very useful thing to contribute.
It's mentioned that the Muslims didn't report the information they found coz they were afraid they'd get in more trouble than they already were, and thus this proves that detaining the Muslims and treating them like criminals is the wrong way to go about the Fayed situation, they should be seeking their help instead. It makes Wayne finalize his decision to reject Tom's methods, leading to the part where Reed Pollock and Bruce Carson assassinate him.
It shows beyond all doubt that Wayne is in the right, and Reed and Bruce, though they believe otherwise, are in the wrong.