I didn't see him acting like a child, all I saw was a guy who didn't want to give up his seat, and rightfully so! It's not HIS fault they overbooked! And, this wasn't even for anyone IMPORTANT, it was for a crew member! You know, the ones who are WALKING around the ENTIRE flight! They have their own seats!
This was absolutely unnecessary of United. I mean, really?! Call the cops because a PAYING customer doesn't want to give up his seat?!?! They handled this ALL wrong. I agree - fuck United.