This sort of logic only works if you assume we are in control of our karts at all times, which clearly is not the case. The solution is to make vehicles that can be safe in INADVERTENT contact and to enforce rules prohibiting DELIBERATE contact. This makes a heck of a lot more sense than deliberately making the vehicle less safe in order to incentivize good driving habits.
Yes, indy and F1 cars are open wheel without “bumpers” but let’s agree that most of us are not at that skill level and are more likely to initiate contact with mistakes and misjudgments.
If more danger made you a better driver, then Sebastial Vettel is crap, since he races with a full coverage helmet instead of a leather cap. And then there is the well-established record of open wheel aces coming over to NASCAR and kicking the pants off everyone (not).
I don’t see much empirical support for the notion that less safety teaches better driving.