Couldn't agree more!100% of the blame here is on the truck driver. He was set up to run that red light regardless if the scooter rider had been there or not.
Having said that, the rider was not very visible in any case. Tiny taillight, black or very dark clothing, etc. I doubt if being more visible would have made any difference in this particular case, but you never know.
I watch my mirrors constantly, but I also think I would not have reacted that fast.