Not sure if this is the way its intended to be, but he dosnt seem to care if you are in fact evil, only giving you the negative dialogue options if you are chaotic after concentrating on you.
The dude in the Helmite shrine and his delivery
I'm pretty certain he's a LN cleric, not a LG paladin.
I thought there were dialogue options for both Evil and Chaotic?
For Evil he says something about washing away sins, and for Chaotic he treats you to his trademark steely glare.
9lives has it.
Does that means he has detect alignment spell?
Either that, or he's really good at guessing!
Anyhow, this is not a bug.