Firstly peoples natures can and do change. People go from Ashtan (considered "bad") to Shallam (considered "good") and were not puppets of the other beuracracy. However that isnt the point.
I think you should consider that even "evil" people need friends, and to turn on them is the path to self loathing.
Thirdly, I dont consider infernals "evil". I consider them to be misguided, some are even honourable, in weird ways (first example raajin who gave me an appology letter for interupting my wedding celebration). So please dont use them in a referance to "evil" or "bad". They are a guild with different people within their ranks, all different. In fact I know two infernals .. who I have only ever met 2 times, once each, to be wonderfull people.

Penned by my hand on the 1st of Sarapin, in the year 245 AF.