Probably just a preference to not have one's innards cut open by said Raider's fans. A good friend of mine brought his daughter to a game and saw an opposing fan get knifed in the gut right in front of him. He spent the rest of the day talking to the police, etc. He vowed from that point on to not be a Raiders fan. Thankfully there were other witnesses, and they only used his report in the case and he did not have to testify.