The boys of Sigma Alpha Epsilon acted badly and expressed ideas that most consider unacceptable. What they did not do was commit a crime. Because it is not a crime to express unpopular ideas.
That's why you can be a Nazi and say that ol' Adolf was a great guy without being arrested. You can celebrate the Boston Marathon bombers with a pretty picture on your magazine cover and not get arrested. You can join the Westboro Baptist Church and say that soldiers are being killed because God hates gays and not get arrested.
The crime committed at OU was the decision by a government body, in this case the University of Oklahoma, to punish the fraternity and expel the students involved for speech that the college president decided he didn't like. Individually the college president can say he doesn't like the speech and that he finds it hateful and distasteful. Using his power as a government official to punish that speech is a violation of the Constitution and crosses the line into criminal behavior.
One of the problems with defending free speech is you often have to defend people that you find to be outrageous and unpleasant and disgusting.