Why? In what ways is Arena Football inherently more dangerous than NFL football? I know in Arena football, most of the players play both offense and defense, so they're exposed to more plays, and theoretically could become more fatigued. Anything else?
The vertical sideline is what would worry me.
In looking at the replay, he did the one thing you are coached from the first time you put a helmet on NOT to do. Go in for a tackle with your head down.