Add in Woodbury, Ellingsen and Gessell just off the top of my head. I don't remember people being racist towards Marble, Jok and Olaseni to name a few.
When you have no valid points to make in an argument just play the race card, question someone's fanhood or my personal favorite "What level do you coach at?" Then of course you put the ignore feature on the person you are debating with.
It's all related to the questioning of character. "He doesn't care about Iowa" and the other nonsense comments. Yes, Woodbury, Gesell and Oglesby and others were all heavily criticized as well, but the comments were never as pointed as they were with Cook.