An organisation is set up which dupes people into giving it money, persuades them of various extremely dubious and unscientific premises about the world, and you therefore give it a tax break. Something about that situation seems wrong to me.

Admittedly some religions do undertake charitable work. However they inevitably also waste at least some of their money on 'glorifying' a being/beings who is/are supposedly omnipotent and therefore quite capable of 'glorifying' himself/themselves. Why not spend it on charities, schools or hospitals which are far more likely to spend 100% of the money on something more useful than cassocks.