I was at that game seated in the AU student section right over the Nebraska players entrance to the stadium. When the opposing team enters the stadium pretty much everyone is looking at them. If this occured, I don't think it could have been more than an isolated single incidence (granted, still one too much!) without me seeing it.
I really hate that your Grandfather experienced this in Auburn. You will find the vast majority of the fans very good natured and hospitable. We sort of pride ourselves in being that way.
I guess it has been said already but every fan base will have a few of these bad apples.
Here is hoping for a great Cotton bowl!
War Eagle!
JN