So, for example, if self-driving cars today drive 10% better than the average driver, this also means that they all drive worse than 40% of human drivers out there.
And? They still drive 10% better than the average driver. And I realize that number is just an example, not intended to be accurate, but I still feel like I should point out that, statistically, it's too low.
The fact that the self-driving cars will all concentrate their worst behaviors in the same regions of the space of all driving conditions doesn't change the fact that, on average, they're quite a bit safer than human drivers. This wouldn't be true if the roads somehow changed so that the problematic-for-self-driving scenarios predominated, but they don't.
I considers these vehicules, in their current state to be too dangerous to be on public roads.
So you consider most human drivers too dangerous to be on public roads.
But I'm sure the usual binary-thinking simpletons will simply put me in their little "against" box anyway
You're taking a binary position (too dangerous to be on public roads), so you should expect people to evaluate your position in a binary way. Your other position, trying to position Waymo safety within the wide continuum of driver safety, is more nuanced.
My position is that if they're statistically safer than average human drivers, which makes them far safer than the worst human drivers on the road, then replacing human-driven cars with self-driving cars makes the roads safer. This is straightforwardly obvious. It doesn't mean the companies shouldn't be held accountable for their failures, and certainly doesn't mean that we shouldn't expect them to to continue working on improvements.