Video says the kid who slapped him called him an expletive as he hit him. You think that was a pat on the back? What would your reaction be if some Republican did that to Biden ( well, actually they would have to pick up the pieces after SS got through with him.
It depends on how hard that “pat” was on a 78 year old. That is not a fellow youth he is doing that to. You can do that very hard with your hand held flat.
Motivation tells most of it. He was taken into custody.
Have to be careful around the old and frail though. Reminds me of my first girlfriends grandfather who decided to start a pulling contest when I shook his hand, I let go, wasn’t about to get in a tug of war with a septuagenarian, he fell, guess who got the blame. He was like eighty, flat on his ass on a concrete driveway with me stammering about it being his fault. Didn’t go over well. Valuable lesson though, doesn’t always matter who’s fault it is in the court of public opinion.