No, it's not just a crotch grab. Jacko was jacking it on stage when he saw a 6-year-old boy in the front row.
Jacko's Stage Antics
Categories
Explanation
Experiment
Explain Bear
Listen up, you simpleton. You seem to think the punchline is that he touched his crotch. No, you dumbass! The joke is that he was doing something naughty when he was on stage, and some little kid saw it. Get it? It's funny because it's inappropriate. You're welcome.