What? According to the screenshot, there's one farmer in the field, and five on the runway. Or, at least, one near a field and five near a runway, but it definitely doesn't say there are five farmers in a field.
Even if the plane can steer and choose to hit either of the two "groups", they have to be physically near one another. The runway must be right at the field, which implies it being a route the farmers take to get to their fields.
It is ethical for someone to act in their own self-interest. With that in, the ethical choice is to pick the runway. Gotta get a higher score,
And you usually have a better chance using a runway, even during a crash