Wishing pain and frustration on anyone is immature and childish, regardless of whom they are. I thought you were the best fans in college football?
I don't know if I really agree with that...saying it's immature and childish. Like KansasHusker above me said, it's a rivalry thing. Whether you have great fans or not...doesn't mean you can't say "I hope KSU gets their a$$ kicked today and their quarterback has a terrible game!" Great fans say that all the time. Hell, I've been known to say that.
But a great fan also understands it is just a game. He doesn't say "I hope the QB breaks his leg" ...or "Let's go get marshmallows, put batteries in them and chuck 'em at rival fans." I think the core of us being 'The Greatest Fans in College Football' is still there. Everyone gets hyped up during the season...and especially so in bowl/championship time. But a true fan knows it's just a game and doesn't take things too far.
However, I did root for KSU. I root for all Big XII teams in bowl season because the better each team does the better the conference looks...and the more money NU gets. Of course, there are the select few teams that I secretly wish for destruction in a game ( **cough** CU **cough** ). You're right, it should be more of a family thing during bowl season. But although a team may be that cousin in the conference you're supposed to love...there was still that one time way back in the day when he 'bad touched' you, so you're bound to hold a grudge.