From the wikipedia article you posted:
"There is absolutely no proof of a hate crime," said John Gill, special counsel to Knox County District Atty. Randy Nichols. "We know from our investigation that the people charged in this case were friends with white people, socialized with white people, dated white people. So not only is there no evidence of any racial animus, there's evidence to the contrary."[
Which takes that quote from: http://www.chicagotribune.com/servic...,5653843.story
Crimes against people of a certain race perpetrated by people of another are not necessarily hate crimes, unless race played a factor in the crime. If I mug someone because they look rich and vulnerable, and it turns out that someone was gay, that doesn't make it a gaybashing hate crime, it's just assault and theft.
I don't know any facts of this case beyond what has been reported in a few news articles I've read previously and the Wikipedia article that reiterates them, but it seems there is nothing to suggest the fact that the victims were white and the perpetrators black is anything but coincidental or that their race motivated the crime.
There's a similar case of black-on-white rape/murder/torture where the hate crime nature of the incident is disputed, and I think it was a hate crime, the murder of Sgt. Jan Pietrzak and his wife Quiana by four Marines.
In that case, there is evidence that the four Marines attacked Pietrzak specifically because he was a white guy married to a black woman and in addition to the money motivation, they resented this and it was why they so heinously tortured the couple. But not only do I not see evidence that the incident you posted is a hate crime, though it's certainly heinous, there appears to be by your own source sufficient evidence that it was not a hate crime. Whether it received less mainstream media attention than it may have if it was a white-on-black crime is a different story, but that has to do with journalistic sensationalism and sensitivity, not the motivation of the crime.