I fail to see how running dirty, broken down fluid is better than running newer more stable fluid. Fluid wears out. The transmission was designed to operate with a fluid whose viscosity matches new fluid, not old fluid. If changing it was "bad", then GM wouldn't recommend changing it.
In an extremely high mileage transmission that has never had a change, I can agree. I've seen new fluid in a 200k+ transmission kill it. However, if that transmission had been maintained with regular fluid changes, it would not have happened. And it would've ran better the entire time.