The point is that no more than 1/3^^^3 people have sole control over the life or death of 3^^3 people. This improbability, that you would be one of those very special people, IS big enough.

(This answer fails unless your ethics and anthropics use the same measure. That's how the pig example works.)

So can we solve the problem by putting some sort of upper bound on the degree to which ethics and anthropics can differ, along the lines of "creation of 3^^^^3 people is at most N times less probable than creation of 3^^^^3 pigs, so across the ensemble of possible worlds the prior against your being in a position to influence that many pigs still cuts down the expected utility from something vaguely like 3^^^^3 to something vaguely like N"?