250 kts is to comply with the ATL RNAV SIDS. But you obviously don't read them.
Evidently some of the majors don't read them either, because their procedure does not immediately accelerate to 250 either. Yes, there are speed restrictions on the departure, but they are to restrict you from accelerating faster than 250 before points, not dictating that you accelerate to 250 at 1001 AGL. Many majors also do not set a speed faster than the limitation for the current flap configuration. My airline does not allow it. In fact, my airline will not accelerate to 250 until 3,000 AGL and flaps are retracted.
Simon's point is valid. It's the responsible approach to managing the automation. His comments are not an attack on your pilotage or your professionalism, but a commentary on how the procedures have been interpreted (not even written) at one airline. This whole debate is over tribal knowledge and technique vs policy. The policy, written doctrine, says 210 to 3000 AGL. You're just told by instructors, flight standards check airman, and LCAs that in ATL we accelerate directly to 250. In fact, it would be a fairly easy legal battle if a pilot was distracted, overspeed the flaps, doing structural damage and crashed. The books are quite clear on what the pilot was supposed to do, but he deliberately disregarded written procedure. But given DoinTime rationalization that the book doesn't tell the pilot how to crash, maybe a legal battle could be won for dereliction of duty if a pilot survives one.
As to the attacks on Simon's character, you'll never meet a better pilot. He has volunteered for ALPA more than most will ever do, and although he is just a line pilot, is better connected to, and respected by, current Flight Ops mgmt. than you might think.