There's no relationship to how fast you go vs. safety. The Germans prove it every day.
As a comparison from the link above, for 2010 we averaged 6.87 fatalities for all roads per billion km (Bkm) of travel in the US, Germany 5.18.
There is a very well established relationship between speed and safety.
If you are doing 30mph down a suburban street and something jumps out in front of you, or some moron brakes for no apparent reason, you have way more time to react than if you are doing 100mph. At 30mph someone might get hurt. At 100mph someone is going to die.
I think we'd both agree that doing 100mph down a suburban street is just me playing reductio ad absurdum, but it's easy to prove that the slower everyone goes the safer we all are. We just have to find a point between "everyone does 5mph and nobody dies, won't somebody _PLEASE_ think of the children!" and "everyone does 200MPH, i'm in a hurry dammit!" that balances safety and reasonable travel times
And I think we'd both agree that averaging 98MPH from coast to coast is too fast. Your German autobahn's are designed for those sort of speeds, and that's great, but i bet the roads this guy was travelling on aren't nearly that safe, especially if the other traffic is going 30-60MPH.