I spend a lot of time writing and talking (here and in my scholarship) about the free speech rights of fans at sporting events. At times, this has me defending yo-yo's who are just trying to piss people off.
But every so often some meaningful speech can, does, and should occur at sporting events. Case in point is yesterday's protest against MLB and Commissioner Bud Selig allowing the 2011 All-Star Game to be played in Arizona. Now, the fans who ran onto the field were wrong and should have been arrested. Similarly, the fans who hung a banner in the center-field batting eye (a place that banners are not allowed) were wrong, although they should have been allowed to hang or display the banner any other place that banners and signs are permitted.
The point is that there is no place more appropriate for a protest of MLB policies, and the politics of those policies, than in the stands at a baseball game. It is an appropriate subject for baseball fans to talk about. And players and other fans are the appropriate audience for the speech. In other words, we need to protect cheering speech at sporting events because that speech often has a real and significant political core. And if protecting a genuine political protest means also having to tolerate some "Yankees Suck" t-shirts or some profanity-laced fan tirades, well, that is the cost of living in a society with free speech.