That "kid" is old enough to know better. He's probably a privileged white upper class, catholic high school brat. He should serve ... time in a reform school. That might straighten him out. It would never happen as his parents are the ones who never instilled "right" in him and would get him a high-priced lawyer to keep him from the consequences he deserves.
Watch the video. The old man is marching into the crowd banging the drum in front of him forcing the kids to get out of the way, until he encountered a kid who wouldn't be intimidated. He could have passed by the kid on the left or on the right, but he chose to stand there banging his drum closer and closer to the kid's face trying to get the kid to move out of his way. His sole intention is to intimidate the kid and make him move out of his way.
Also, listen to the entire 3:44 video. I didn't hear a single "build that wall" from anyone there.