This is only true in a very theoretical sense. Going 180 km/h will 9/10 be more dangerous than going 120 km/h. Reaktion time, brake time, requirements to equipment, everything is tougher at higher speeds.
The correct conclusion is that the safe speed directly depends on the present conditions, and depending on that, you can be going unsafely fast or unsafely slow (or both, if you’re drunk or inattentive).
https://www.google.com/amp/s/www.thelocal.de/20190201/are-ge...
The desire to minimize the speed at which crashes happen literally costs lives when applied in the real world because reducing the frequency of crashes is the superior option.
While I understand that minimizing crashes is important, I'd rather be faced with scenarios where we crash in a manner where people survive more often - any accidents that do happen at the higher speed is going to skyrocket the chances of a fatality.
It's too bad the civil engineers working as traffic engineers absolutely refuse to actually follow the recommendations of these studies. Honestly, I can't think of a more intellectually dishonest profession than civil engineering (specifically, the traffic engineering subset of it; the guys who build buildings and bridges are OK).