the repeated "crossed state line" talking point coming from the media really is about the state of things.
It is not, nor has it ever been, illegal to carry a gun across state lines in this country. Yes, you need to know the laws of the state to which you're traveling.

This is true, but in the context of the Kyle R. trial, it is brought up as intent. That is, he intended to use the firearms offensively (ending his self-defense defense). The counter argument here is that a court of law found him to be innocent of that which means that anyone continuing the "crossed state lines" nonsense is making a slanderous and libelous statement. People can say it's their opinion all they want, but that is only valid before the trial. Once the verdict represented him as innocent, it became objective fact that he did not. Anyone saying otherwise is now legally responsible for their statement.