I wonder how many times this guy got his ass kicked by pre-teens before he was able to pull this off. I picture him standing in front of his mirror, screaming, smacking himself in the face and tearing his t-shirt…and then he want out and finally did it. The hat is his trophy, now. You can see the joy in his face.
Don, Jr. is looking back like he's asking your for a rubber on prom night.
It's a defensive grip designed to limit the other person's ability to squeeze your hand really hard. Essentially, it's posturing so they other person knows you're not a pushover. Notice RR isn't doing it.