It makes no difference one way or the other. The idea is that customer A doesn't want their campaign paired with ads from customer B. I don't care whether they're right or wrong in feeling that way -- they clearly do feel that way. So if you do it anyway, you are absolutely making a clear choice that you favor customer B.

That's my only point. There's no way to abstain and keep the goodwill of everyone.

Basically, yes.