Specifically, Irvin doesn't like the way Parcells referred to Owens as "the player," rather than calling him by his name. Irvin had this to say to a local TV station, as reported by NFL Network:
"I think it's one of the most disrespectful things you can do. You go to work every day and your boss refuses to call you by your name ... you would have a problem with that. ... I wouldn't have liked playing for a head coach like that."
The one thing Irvin doesn't mention here is that he has a reason to have ill will toward Parcells: ESPN fired Irvin and hired Parcells this year.
Still, Irvin has a point: As great a coach as Parcells is, he has a propensity for acting like a jerk toward some of his players, and just because Owens is a bigger jerk, that doesn't make Parcells blameless.