I think we should not be satisfied with merely “better than a human”. Flying is so safe precisely because we treat any casualty as unacceptable. We should aspire to make automobiles at least that safe.
But the question was when should we allow autonomous driving on our public roads. And I think "when it's at least as safe as the median human driver" is a reasonable threshold.
(The thing about Tesla FSD is that it -- unsupervised -- would probably fall super short of that metric. FSD needs to be supervised to be safer than the median human driver, assuming that's evn currently the case, and not every driver is going to be equally good at supervising it.)
The question is whether you want to outlaw automatic driving just because the system is, say, "only" 50% safer than us.
It’s a net positive, saving lives right now.