I don't understand why this keeps coming up. I have never seen or even heard of a driver getting into a situation where there's any sort of moral dilemma in how they react. There's always an obvious best answer or a bunch of equivalently good answers.
For the one-in-a-trillion cases where this is not true, it's OK if the car reacts sub-optimally. It will still be vastly better than human drivers, who frequently react sub-optimally in unambiguous situations.
There are physical limits on how fast or smart you can make braking.
We make thousands of unconscious decisions while driving - many of them moral/ambiguous. "Should I pass this car in the intersection even though it is breaking the law?" "Can I squeeze past this bicyclist even though it forces them towards the curb?"
The core of most of these arguments assume a fully autonomous world - and it just won't work like that.
