Deer vs little girl does not really matter, that is just an emotional ploy.
I guess once these cars begin being sold people can start testing situations using dummies and such.
That said, there are certainly circumstances where swerving is the right decision and a vehicle with 360 degree sensors is potentially in a better position to make an optimal decision than a human making a snap judgement based on mostly what they see in front of them. Probably the closest I ever came to being in a really serious accident happened on a highway when someone slammed on their brakes to avoid rear-ending the car in front, ended up drifting into the next lane where another car had to swerve to avoid them. I ended up swerving into the breakdown lane. Amazingly with cars swerving and braking all over the road at 70 mph, no one collided but it was a very near thing.
I strongly suspect that, however many decades away true self-driving is, good assistive driving and collision avoidance systems especially on highways are going to be a pretty big near-term win.