Sounds like sick propaganda.
This is exactly right. Yes, they expect the audience to laugh and cheer as "hate" Christians are being viciously murdered with great violence and efficiency.
It *was* sick propaganda designed to normalize the idea that Christians ought to be murdered.
The Church members were victims of the bad guys final field test. Everyone on that church was affected by the weapon. When the protagonist realizes what has happened, he is obviuosly filled with revulsion.