Because he thinks that Fred would have stayed an extra year and would have further set back the basketball program by not doing the entire job.
Personally, I think that had Fred wanted the Timberwolves job, he could have gotten it 2 years ago. I don't think Flip really wanted to coach, but when they didn't get Fred he took the job.
I'm not sure exactly how you can argue that Fred ever did anything to set us back. If he would have waited we would simply have a longer streak in the top 25...