Throwing popcorn is not deadly force.
"The person who happened to be 71 has the right to defender himself."
No, you cannot use deadly force to defend against an non-deadly force attack. Sorry. If you do it you are going to find yourself charged.
If you believe you are under attack which he was, you don’t have to delay a response to see if the attacker will stop.
When your 71 being hit by fists can be life threatening.
The texter guessed wrong. Good riddance.