muffin, I dont think anyone has said the motorcyclist wasn't in the wrong to be doing such speeds, but other than acknowledge that, how can he take any blame? he is dead!
Just because he's dead doesn't mean he wasn't to blame 
Even if he hadn't been doing 90+mph, he still would have come off his bike and been injured, quite possibly still fatally.
I didn't say he wouldn't have been, or at least I don't think so now, having re-watched it. The driver is to blame, the biker is to blame.
His speed was not the cause of the accident.
It was a contributing factor, surely. Maybe if he was going slower there may have been some wiggle room. I don't know this or the road but there's a possibility, surely, that doing 2/3rds the speed limit contributed to this?