Simply put, pessimism is expecting the worst. Expecting that the team will win no more games is pessimism.
Negative is seeing only the worst in things. Seeing 9-9 in conference while ignoring 20 wins and the 7th trip to the NCAA's in 8 years is negativity.
Does that satisfy you?
That helps a bit. His post was specific to the trajectory and recent play of the team, which is most relevant to their potential success in Big 12 and NCAA tourneys. You think we should blindly expect future wins without taking anything else into consideration?
At this point I would say it's being realistic. The team lacks an identity on either end. Very inconsistent cohesiveness. They haven't demonstrated the details and little things that it takes to win games and beat good teams.
I hate to admit that and see my favorite team play so poorly. It's discouraging that the coaching hasn't been better, especially when it comes to protecting our proud home court.