How does that compare to the number of deer/miles traveled of "regular" cars? That's the important part.
If you live in deer country you know how often you see dead ones on the side of the road, it's just scandalous because it was a car on autopilot, but if it's still safer per miles traveled than having humans behind the wheel then it's still a win.
If it had braked and just couldn't stop it would be comparable to a person. Continuing at full speed into a solid object on the road is the same as the worst human driver.
If it wasn't limited to only cameras because Musk is an arrogant jackass then the lidar/rader/other non-camera sensor would have sensed the deer being an object even if the camera didn't recognize it.
That's one example, do you seriously believe there are no cases of human drivers not slowing down before hitting something because they're busy checking their phone or they're DUI?