Perhaps, to fulfill Arions point of the 'Morally Grey' viewpoint, these angels could be vicious zealots? Perhaps they are indeed bent on the persecution of Chaos, and find more Morally Upstanding people and allies among the sentient races of Man, Dwarves, and Elves, and may even have an inbuilt prepensity to ally with those nations.
But, how about if that trust is easily broken, or if they simply live by the code of Saito Hajime (An anime character) which is 'Ack Suku Zan', (Forgive me if I got the spelling wrong, It's been a while. It's correct phonetically, though!) 'Destroy evil imediately'.
such as, Allied with the race of Man/Dwarf/Elves, and at the first sign of unrepentant corruption, they're destroyed. Perhaps in such a spectacular fashion that it cannot be denied, and throwing their blatant disregard for human/sentient life into the mix that their moral boundaries are blurred.
My two cents, as a guideline against making them the 'Goody Two Shoes', but perhaps a race of super aggressive purists.