Trump didn't walk into the debate with plans to give military commands to the Proud Boys. Wallace asked him to ask them to "Stand Down." It becomes somewhat chaotic with Wallace and Biden attacking Trump. He says, yes I'll tell them to stand back. He clarified he meant "Stand Down" the following morning.
You have 2 options. Either, Trump got the word wrong... said back, tried to correct, said by... then stopped trying to correct. A word fumble. Or, Trump purposely instructed groups he is actively arresting to prepare for attack. The 2nd option makes no sense.
BTW.. I didn't even notice he swapped stand down with stand back. I just saw him agree to what Wallace was asking. It wasn't until the following day when I saw the left spin this up that I even realized there was a problem here. In my view, the left took a small fumble in the middle of him condemning these groups and make the fumble into the story.