Not very professional to call your vendor incompetent on creative content when you use their idea. I don't think either of them come out smelling of roses here

Not very professional to call your vendor incompetent on creative content when you use their idea. I don't think either of them come out smelling of roses here, but an ad agency relies on reputation. If a paying client threatens their future revenue by badmouthing them, they're left with two options: 1) say nothing and have future clients think they're incompetent 2) defend themselves and have future clients know they are competent, but won't put up with some of their client's BS. Neither choice is ideal, but maybe #2 defends their reputation at the same time that it filters out clients that will spout BS like this. Fewer potential clients, maybe less revenue as a result, but more revenue than if clients thought they were incompetent.