As long as other cars (or humans, or animals...) are on the road, robot cars will face these scenarios. The OP's scenario is contrived to make a clear example,

As long as other cars (or humans, or animals...) are on the road, robot cars will face these scenarios. The OP's scenario is contrived to make a clear example, but it happens regularly when you're driving: you're forced to make a choice between acting and possibly hitting something, or doing nothing and being hit. We don't need self driving cars to solve the 80% case of preventing human drivers from hitting things. We need radar and auto-braking, which already exists. Full autonomy requires solving the harder problems.