Not going to disagree with the bolded, and the cops handled it fine. But it's not like he was walking around NYC like that. He was walking around Grand Prairie. I'm not saying it's a good idea either way just giving it some context.
The guy probably thought it'd be uneventful to walk over to the tailor in his gear
Now if this was in the heart of downtown NYC, Toronto, Chicago, etc, I'd think he was a total moron. It's a small city though, I don't think he realized it would be taken that way or that so many people would see him and make that assumption. He's probably pretty young too, didn't understand how his cosplay could be misinterpreted.
Again though, not a good idea, I just can understand why he'd think it would be okay. Cosplayers often think their outfit looks a lot better than it actually is.
What they see when they look in the mirror:
Reality: