Because
Because... so many depended on his actions.
Because... he had a job to do.
Because... there really was no other choice.
Because... regrettably, he had to order Carter to make it.
Because... there was no more time.
Because... Daniel had been so damn stubborn.
Because... Daniel had to live... so HE could kill him, slowly.
Because... despite orders, he absolutely trusted Daniel.
Because... he would have to be the one to press the button.
Because... somehow he knew Daniel would be okay.
Because... afterwards he knew he'd been right... again.
Because... Daniel came through it safely and found the solution.
The End
