Seems like they have a small group of fans who have a chip on their shoulder and would rather see an OU loss than an OSU win. Most are pretty good fans with quite a few who believe they are closing the gap on the most lopsided in-state college football rivalry. They have had more success against OU in the last 10 years vs. the previous 70 or 80, but they still have a long way to go and will be "little brother" for a long, long time, which irks them.
But, to their credit, they do have many trophies, conference and national championships in baseball, basketball, wrestling and golf. They don't have as many conference championships (in all sports) as texas, but they have quite a few more than OU.