That's a Strawman argument though. Nobody is going to say that simply being on the field will justify being struck.
The argument will be that 5,000 people being on the field, all of them very excited and quite a few of them also drunk and screaming about "redemption", creates a hostile environment...and Is beyond the ability of UT security to provide for the safety of the visiting players. And that UT is at fault for failing to control this.
There is precedence for this perspective. Just this Sept 21, Texas Tech fans stormed the field and assaulted a visiting player (and are being fined).
Video of Texas Tech fan pushing Texas player illustrates the risk of continuing to schedule the Red Raiders
And remember "Malice in the Palace?" IIRC, the Detroit law enforcement ultimately did NOT prosecute Pacers players because the Pacers could reasonably claim they were in legitimate fear for their personal safety after Pistons fans came into the court. And this was despite players going into the seats to beat the stuffings out of a number of fans.
This is also why cops escort visiting coaches off the field after games. Visiting teams can feel threatened by a mob pretty quickly.
I sure as heck wouldn't have wanted to be down on that field wearing an Alabama uniform after that buzzer sounded and people started pouring onto the field.