Yeah, interesting, but frustrating. I'm not a fan of the cops, but I also respect the position they are put in. This is America, Second Amendment, blah blah blah, but realistically, I don't blame someone for calling the cops to investigate some dude walking around with AR, not on the shoulder, but slung on front of him, walking down the road. And once the police receive this call, they are not going to make a judgement call over the phone & tell the 911 caller not to worry about it, it's probably just someone making a point, exercising his rights. Cop(s) arrive at the scene, you put yourself in their shoes...... this could easily go south, potentially crippling you for life, or kill you dead. You can expect them to be professional, but they may be bit tense.
This "soldier", I respect what he does for the country & everything, but I think he's being one pain in the ass(that's how they talk down there, right? lol), putting the police officers on the spot. I can only judge from what I saw on the video(saw most of it), but he was being whiny, rude & insulting to the police, where if I was in his situation, I'd be calm, respectful in explaining my situation. I'd politely ask for their understanding, also apologizing for forcing them into a tricky spot.
I don't think the guy should have been arrested in the end, but like Nicksfix said, we didn't get to see the whole story. I thought the cops seemed reasonable with the exception of the arrest at the end.