The way I run things is that corruption points come from warp/ruinous powers exclusivly.
If Hitler and Mengala (both would have existed in 40k cannon) didn't grow third arms out of their foreheads then neither do the characters for any non warp related evil. However acting like a sociopathic murderer WILL gain you insanity points. Act like an insano for long enough and you just might become one.
As to doing evil deeds atracts the attention of the ruines powers and thus gains the character CP I think is dangerous. Where is the line? Since the chaos gods are basically made up of the bad/evil of sentient races then almost everything the acolytes due would fall into their hands. Lying, killing, etc,etc. virtually every thing they do would please one or more of the chaos gods and would thus earn them CP and VERY short carrers.

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