So much this. If we aren't going to restrict possession of firearms in any way then we can't use that as a basis for intent. Just replace, "had a gun", with literally any other constitutionally protected right and this argument falls flat on its face.
"He was using words, we will never know if he was about to run into a theater and yell 'fire'..."
What you are talking about is colloquially called Chevron Deference. And yes, it is on the kill list after Roe, Obergefell, and I can only assume Brown v Board ffs.