Well, it’s not as simple. The humans can still destroy the baby-eaters even they have deflectors up, while the baby-eaters can’t destroy the humans if they have deflectors up. So it’s not true that “putting up one’s defectors does not hurt the opponent”. Putting up the deflectors breaks the symmetry, and makes the humans in a position of dominance, while not putting them up is a token of trust and maintains the situation as symmetrical.
Well, it’s not as simple. The humans can still destroy the baby-eaters even they have deflectors up, while the baby-eaters can’t destroy the humans if they have deflectors up. So it’s not true that “putting up one’s defectors does not hurt the opponent”. Putting up the deflectors breaks the symmetry, and makes the humans in a position of dominance, while not putting them up is a token of trust and maintains the situation as symmetrical.