The Saints forum let me in no problem. Probably since we're not rivals. I'm actually surprised this forum let me in considering Green is Jets/Eagles colors.
We give the benefit of the doubt to people... that said, if you start stinking it up (in terms of actual spamming, not just rooting for another team), you could have GIANTSFOREVER as your username and still get banned.
I'm Commander Shepard, and this is my favorite team in the NFL.