"America is still a nation that [...] sent a brave young man from Ohio [pause...] to a [pause...] PLANT! You know who it is, the stars and stripes on the face of the moon, you know who it is"
He couldn't bring himself to say what the teleprompter said because he knows it's not true.
That's possible also, but why did he stop reading the teleprompter and change the phrase so deliberately?Sent a man to a plant?