The part where they are deliberately choosing to endanger their fellow citizens?

Damage scales with the square of speed. Speed limits aren't put in place for fun, they are there to reduce the number of accidents. A speed limit says "Accidents are likely, slow down to reduce the severity of them". Hitting a pedestrian at 30 km/h means they'll be injured, hitting a pedestrian at 50 km/h means they'll be dead. If you're speeding, you're essentially saying that you arriving a few seconds faster at your destination is more important than someone else dying.

On top of that, a difference in speed greatly increases the number of accidents. If everyone drives at 30 km/h, that one person at 50 km/h will constantly be tailgating and overtaking. That is far more likely to result in accidents than simply following the car in front of you at a safe distance.

The enclosed nature of the car is what does that.

I think you misread this. The point was that >95% of people drive over the speed limit because it feels right, not because they’re sociopaths. Making it feel wrong to speed is sufficient for most people.