Now, let's go back and look at what you wrote. First there is:
"a throw-down gun that McDonald brought"
This is a positive statement that you provided no supporting evidence. That is to say, an assertion.
Nope. What Mr. Iacoletti wrote, in response to a
suggested scenario from Mr. Zeon Mason, was:
".or Oswald didn’t have a revolver at all and the gun that was struggled over was a throw-down gun that McDonald brought."
He was offering an alternative possibility, not a 'positive statement'. By leaving out the 'or' you have distorted the sense. I guess you'd call this 'compression'.