Bruce was angry with Campbell after he allegedly told the club he was "nipping out for lunch" but then walked out on a potential move to the KC Stadium to hold talks with Blackburn Rovers.
The whole affair left a sour taste in Bruce's mouth and he blasted the striker of a lack of professionalism.
Bruce raged to the Daily Mirror: "The total lack of respect by DJ and his agent left a bad taste. I have no problem with him going but the way they handled it is shocking.
"They said they were going for a bit of lunch, but went along the M62 and left us trying to find out where they were for a couple of hours. If they had rung and said what happened we could have all got on with our lives.
"I have been in the game for a long time and never been as disappointed as I am with their behaviour.
"It's just greed. Be a man, just inform us of your intentions."