Where did I say that it isn't valid?
I wasn't ever questioning that blacks aren't sentenced to more than others for a similar crime. I'm simply stating that you can't throw a blanket on the subject and say "Well, it must be white racism." The issue is that you guys honestly need to stop drawing your own conclusions that the statistics clearly don't support. It was never meant to draw a conclusion as to what the causation is.
That's the thing though, the statistics DO support that. I'm not sure how much experience you have with stats but I have quite a bit. There will ALWAYS be variables you can't account for but the finding in this case is so large and so robust that it is very unlikely that race is not a factor. Furthermore multivariate analysis NEVER draws conclusions as to causation. For example research would never attempt to say that smoking causes cancer, it would simply say that they have found a large relationship between the two that's unexplained by other factors.
So yes, we can never know for certain but we can say what the evidence suggests, and it suggests racism.
The point is that there is a multitude of factors you need to account for - there are MANY different reasons why conclusions are made. Simply stating the world is racist doesn't solve the problem or assess what the culprit contributing factor is. Quick example could be our previous discussion: Blacks are substantially more likely to be single parents (most often from the father leaving). Do you think a judge would have more or less sympathy for someone taking care of a child or not? Again, that is one of MANY.
Just because every possible factor cannot be accounted for doesn't mean that the evidence isn't strong. For example in your case since single fathers are quite rare in both the black and white communities if single parenthood were the cause then disparities should largely disappear when it comes to male defendants. It does not.