It depends, I once thought of using some mindless xian to attack someone, but their prayers feed their "god" (thought forms), and essentially the energy they gave to their "god" is not necessarily going to affect their targets.
The energy of the thought forms goes to the targets chosen by those who control the thought forms, the xians give their energy to the "Jewish god" and then hope that energy will affect the target.
If the xians pray for the end of war, the enemies who control the thought forms will never use the energy for that, instead they link the thought forms to the war and cause even more misfortune, the xians don't choose, they just energize the thought forms.
A slave does not choose, his master makes the choices.
If a Xian prays against a Satanist, the enemies will be more than happy to connect this energy with the Satanist.
If I used xians to attack someone, my target would not be affected, and those prayers would only feed that false "god".