It comes down to one simple fact: People don't like Shawn. Point Blank. So any chance they get to cheer on his failures, they will do so.
They didn't like him when he was competing, they didn't like him when he retired, and they probably never will.
Anything that is seen as a failure for him is cause for celebration. I bet a lot of the people who are ragging on his promoting skills never went to the Colorado Pro or even heard about it. They just wanted to bash Shawn.
I'm not his biggest fan, but I think what he did was admirable. At least he tried to affect change in bodybuilding by promoting a show.