Terrorists do not value lives, not their own, not their countrymen. If the U.S. was guranteed to kill tens of thousands of their own countrymen in retaliation it would not deter them. That would just improve the supply of willing terrorists commitmed to their cause.
These people serve Turth, and no one who serves Truth, whether it be Islamic Truth, Christian Truth, or The Great Comet, can be expected to act rationally or with any consideration whatever for human life.
Truth is absolute and immutable, and all else is irrelevant.
In truth, to call Servants of Truth pigs is to insult pigs, which are a lot more rational and probably cleaner.