Rivalries bring a whole other aspect to the world of sports. It isn't a game anymore, it's almost life or death. For MSU and U of M, it's easily one of the most important games of the year, EVERY year. No matter how bad the other team is, bragging rights are essential for that year.
Some people can take rooting for the team a bit too seriously. Their trash talk reaches a limit that no one should be at. When you start getting angry and bringing down fans of the other team, that's when you stop. The night that U of M won, my friends were arguing on Twitter about the game and one decided to say, "Well you don't and never will go to either school, so it doesn't matter what you think". I jumped in REAL quick. Just because you don't go to that college means you can't be a fan? All right, well that means no one can go to any games anymore except the "STUDENT" section. It made me and the friend he was insulting very angry. I ended up burning his Michigan State lanyard though, so it's all right now.
But like I said, rivalries can be really awesome, but some get taken too far. People need to know when to quit.

Oh you know, just burning an MSU lanyard