I think an insider might actually be more frustrated with Bowden than some of us fans. He sees how Bowden treats people day to day whereas we just hear it sometimes second hand.
TC critizes Bowden as a person a lot but I think in general it is well deserved. I have seen far fewer people criticize Bowden the GM. In general, he is a low payroll magician, making us over the years far more competitive than we had any right to be.
Many people, TC included, criticize Bowden for his biggest weak spot, the "5-tool" OF. But I think in general, that is because he is searching for the diamond in the rough. It is far easier (not easy by any means though) to develop baseball skills than it is to make a guy run faster or throw harder. Still, that has to be Bowden's biggest weakness.
To sum it up, we see Bowden the GM and hear a little bit about Bowden the person. Anyone close to the team is going to see a whole lot more of Bowden the person and since that is his biggest liability, they would obviously think less highly of him than a normal fan might.