What was the rationale in making pretenders un-Blessable?

[Sombre]

I think Edi basically covered it. Having faith in something gives you power, but who is even to say the power stems from the thing you have faith in? Dom3 suggests it does by bless relating to their magical power, but perhaps it's the other way around - the belief of the people and practices of their sacreds (having flaming weapons, regenerating etc) shapes the magic power of the pretender.

Think about sects and denominations. They don't practice the same religion, but they usually have faith in the same godhead.