As he pointed out, the bulky item was the pump. There was no reason for him to have to open his belt, be patted down elsewhere, etc.
The only problem with this rationale is that if the insulin pump alarms the walk-thru metal detector (and many do), it's impossible for us (screeners) to know if it's ONLY the pump that's causing the alarm, unless we do additional screening.
After all, you could have an insulin pump, AND a gun in your pocket!
And our standard secondary screening procedure calls for using the hand-held metal detector and doing a quick pat-down.
Yes, going through the checkpoint IS a bit more complicated for people with implanted metal or attached devices, but I just don't see any way around the issue at present. Hopefully someday, we'll have better and less invasive technology!