Your arguement is based on the idea that Borknagar WAS good, and
was your friend, etc..., and eventually turned to evil. The reason
I say this is because for a good man to lie and cheat, etc...would
indeed be horrible. But I contest that Borknagar was bad from the
start. And for an evil man to lie and cheat and decieve, it is
in their nature to do so. I would suggest that you consider
Borknagar as a infernal who acts friendly to the paladins. If
such an infernal turned from being friendly to being evil would
you look at him as you Borknagar? I don't believe so.
Now I may be wrong, but this is how I expect people to act, each
in accordance to their own nature, whether it be good or evil.
And being upset with an evil man for being evil and doing evil
things is like being upset with the wind for blowing or the sun
for shining.

-Dream

Penned by my hand on the 24th of Mayan, in the year 244 AF.