That guy who ran out there could sue that security guard and probably win. The use of force by the guard is not commensurate with the infraction. No one was in immediate physical danger of that guy running on the field. The use of force by the guard was unnecessary, excessive and unwarranted.
It was awesome to see...just sayin'. You know how people are in this litigious society we live in.
It could easily be argued in court that the security guard could have easily stopped the guy without using that kind of force and that he should have at least tried.