Aziraphale could so easily have been in the same boat.
*nods* Aziraphale and Islington both thought they were doing the right thing - still do, really - and while it's not all that evident in Aziraphale's case ('though I think it's still implied), they both were wrong, inasfar as 'right' was decided by Heaven. Er. I think that sentence got away from me a little.

It is only right that he should have compassion other angels who have lost their way.
And actually, depending on how you read his character, Crowley could almost be included in that as well.