The distinction between "near" and "far" thinking seems to have a connection with the old distinction between a puzzle and a mystery.
(Quick recap: A puzzle has a definite solution; a mystery does not)
Near thinking is outstanding for solving puzzles, but breaks down when examining a mystery. There is too much that is uncertain and unknowable about mysteries to allow close analysis to provide useful conclusions.
When examining a mystery, the less rigorous, more intuitive nature of far-thinking is more useful. Where there is no definite solution, one must speculate in a somewhat irrational way in order to form an action plan.
General George S. Patton said, "An imperfect plan implemented immediately and violently will always succeed better than a perfect plan."
This is a brilliant parable on behalf of possibility, but it doesn't end the argument (as Eli freely admits) because it doesn't have bearing on probability.
As a surface analogy, it makes it pretty clear that discontinuous and radical, even unbelievable change is possible. But it doesn't make it probable.
One last wrinkle:
I think that it's important to understand the value of selectivity. One simply doesn't have the energy and time to make an extraordinary effort at all aspects of one's life.
Pick a few areas in which to make an extraordinary effort, and focus on getting by everywhere else.
Methinks Elie is making to too easy on his human characters. I actually don't feel much emotional angst over the babyeaters because they are so alien. After all, plenty of species on Earth practice cannibalism, yet we don't go on a crusade to exterminate them.
No, what he really needs is an alien race that consists of cuddly mammals, or perhaps an offshoot of humanity that evolved this practice of spawning and culling.
Most people wouldn't feel horror over crystalline entities eating their young, but they would go apeshit over human beings doing the same.