I am certainly not defending Owens for what I believe to be a terrible error in judgement, but if you consider his first (at least the first that I know of) shot at McNabb, I think Owens's comment was very understandable.
The first comment, when Owens said that he was not the one who was tired at the end of the Superbowl, came after Owens was asked in an interview what he thought of his critics who said that the Eagles were able to get to the Superbowl without Owens and that maybe he really wasn't a big difference maker for the team.
Put that in the context of Owens's hurried rehabilitation, risking his career by playing, and disappointment/anger over the Eagles FO's refusal to renegotiate his contract, and it is easy to understand why this man of huge ego would lash out. In light of McNabb's physical breakdown in the Superbowl and the fact that he is perhaps the only player that has ever been treated generously by the Eagles FO, it is clear why McNabb was the target of TO's frustrations.
The bright side is that if TO's actions are explainable, it may be controllable.