I feel I need to quote a great man, Homer Simpson, and fan behaviour at sports events:
"It is my right, no, my duty, to make a complete ass of myself."
Seriously though, I got one of these letters, and from what I take from this article, you must get arrested/tossed in order to have this happen to you, and since I have never even been spoken to by event staff or the sheriff, I assume that my behaviour is within the acceptable limits. I am loud and cheer like mad, while taunting any opponent fans near me, but never in an offensive way. It makes me wonder, what kind of insanity you must be involved in in order to be punted from the stadium.
I respect the NFL doing this, as it is a family game and that's how they want to be preceived, but they are walking a thin line, as you don't wanna quell the fans' passion. But so far I see/have no problem with the policy, and the letter serves as proof they are serious. Tread carefully...