Not siding with him, but we don't know what the situation was. I had a heart attack come on while driving at age 39, so I drove kind of quickly to a hospital when doing so. Also had our toddler stop breathing and start turning blue while driving, same thing, I pushed the pedal through the floor to the hospital while my wife jumped in back and started to figure out what was happening.
If his truck actually reached 80, then he absolutely modified it to drive that way, it is unsafe, and it is unlikely that it was an emergency. When I used to see somebody far exceeding traffic speed, I used to quickly think "Geez, what an arrogant POS", until the above items happened to me, now I simply stay out of their way, and realize there is a 1% chance of a real situation occurring.
I'm not defending this guy. On the same token, do we have any known cases of our tires letting go at speeds over 55mph (their rated speed @ load)?