I'm not sure where "truth" fits in, but loyalty is part of honor to me. To go "well, you did something I don't approve of, therefore you are no longer my friend" seems wrong to me, honorless. It has to be really bad before I would make such a decision. Loyalty, sticking by the people one has chosen to stick by, seems more important to me than the personal-honor thing which would require one to disassociate from any "stained" person on principle. It's like hey, you said you were throwing in your lot with them, and to withdraw that is breaking a commitment... I guess it can come down to what are the criteria for what's "bad enough". Could that be where "truth" fits in?