I don't see anything wrong with it, I don't see it glorifying violence anymore than movies like Gladiator or 300 glorify it, it is what it is, shit to psyche up the crowd and get them pumped. I doubt it had anything to do with the the history of gladiator combat and all and more that it's cool and synonymous with toughness.
Lets be real here, it hardly has anything to do with that anyways and we know it. Guys paid a lot of money get NFLers to wear their helmets so that kiddies will go and buy them themselves, gotta protect the brand.
Same thing with the fining people for using headphones that aren't the company sponsored ones.