Your observations are correct, but the reasoning is off a little.
The reason black on white isn't reported is because the media likes to keep it covered up. It isn't just the Jena 6. There's the Carr brothers, the Zebra murders, the attack in Long Beach last Halloween, the Fairmount murder, and so on and so forth. The media doesn't report these things. Most people have never heard of any of them. They do it because only whites can be racist. When whites do something that appears to be racially motivated, it's all over the news. The Duke lacrosse thing is a good example - the media already had them convicted.
You should be thankful the vicious black on white attack in Jena isn't front page news, for it, and the black community's support of those criminals, would only help my cause. Most people know that there are different degrees of severity. The white kids hurt no one. That's why they got off light. The blacks, though, viciously attacked a white. 6 blacks attacking 1 white. That's why they're facing much more severe punishment. Most people can see the difference between a prank in which no one was hurt and a gang viciously beating someone.