Let's say you have friends who occasionally invite you to lunch or suggest having a few beers after work.
But it never fails that these people also invite someone you can't stand. So you always decline the offers.
Inevitably, people will stop inviting you. So would it have been better to have said, "You know, I'd really like to go. But I know you also have invited Nutly. And while I have no interest in bashing him, because I know he is your friend, I have to tell you the guy rubs me the wrong way."