I can't see how Apple making a Bluetooth controller, which, say looked a bit like a PS3/360 controller, and selling it as an optional accessory could be in any way a negative thing.
No-one would be forced to buy it, and no devs would be forced to support it.
Apple could insist every game have on screen controls for people who wanted to only use the touch screen for gaming.
But apps could support the external controller also.
This could only be win win for Apple and users.
It's adding additional functionality and adding the possibility for more advanced games to be developed for the device in the future, esp as the speed will only get better as new iPad's come out.
Not doing so, almost feels like they wish to cripple the device forever.
Why would anyone say they would not want Apple to give users and devs the "Option" of something like this? Not force people to use it, but sell it as an "Option"
If they do this then the iPad had a chance of becoming a genuine serious gaming device in the home in the long term. If they insist forever to only support touch screen, then the iPad will always remain that thing which plays cheap and simple games.