I'll throw in my two cents here....
Last season, I went to Columbia to watch Ole Miss play Mizzou. My buddies and I wore red and blue and cheered for the Rebs. We parked in the lawn of a frat house and tailgated a little bit at the stadium. We sat in the Ole Miss section, and as there were only a few hundred of us Reb fans, we were not only surrounded by Mizzou fans, but had quite a few of them in our section. My overall experience was very good; there was one loud-mouthed fan who kept giving a Rebel fan in front of us a hard time, but he was doing this in a relatively polite, fun manner. At the end of the game, the two guys shook hands and said, "Best of luck" for the remaining season. Overall, the Mizzou fans were very polite and showed great hospitality. In fact, I found the students to be nicer than the adult fans.
Well, needless to say, my experience was quite a bit different this year when I watched Mizzou play Nebraska. A lot of the fans were straight up jerks. Cussing, taunting, and poor sportsmanship were abundant. A few Husker fans fired back, which certainly didn't help the situation.
I have also been to quite a few games in Lawrence. In all the blow-out games I've seen there, even with KU winning, the fans were there for a good time and often left when the outcome was certain. I did find the student section at KU to be pretty rowdy. They have a tasteless cheer, "Rip their f****** heads off!" when KU kicks off. But still, nothing too bad.
Again, this year's KU-NU game was quite a bit different than other games. A lot of fans were more hostile than normal and I witnessed Husker fans taking their fair share of abuse. (I would also like to add that even though certain sections are titled "student", many college-aged kids from other schools like to come down to see some old friends and cheer for their visiting school.... no excuses for fans' bad behavior towards other teams' fans sitting in the student section).
My point about all this: Big 12 schools get more pumped up for Nebraska games and take them way more seriously. I don't know if it's the fact that Nebraska is still viewed as "The football school" (along with OU) in the Big 12, or what, but when Nebraska comes to town, it is a completely different experience. Maybe opposing fans find it intimidating to see a quarter of their stadium filled with Husker fans and feel the need to act obnoxious. I don't know.
These are just my personal experiences. Take them for what they're worth...