I think that there is a very big difference in association as you are using the word and the alliance of convienance applied by the use of the word association in the context. It's that alliance of convienance that Roy is potentially guilty of - of looking the other way when evil is performed because it would be convienent to overlook it. Paladin's aren't 'ends justify the means' sort of people. They aren't allowed, as Saruman put it, to, "deplore evils done by the way, but approve the high and ultimate purpose."
Obviously, if the lawful good party in question isn't looking the other way at his companions behavior and treating it differently than he would treat it if it didn't seem so much easier to achieve the 'high and ultimate purpose' by doing so, then the association isn't tainting them in any way.
But thanks for the straw man. I should start collecting them.