My vet (who I like) once told me I was going to make an enemy of my cat by testing so often. In a very no-nonsense voice, I looked her square in the eye and calmly told her that Sam doesn't cry or flinch when he's tested, never runs from me, instead he sits calmly on the counter without being held and usually purrs through the whole thing AND that while she might not agree with it, he was my cat and as I was the one paying his bills, I was going to do what I thought was in his best interest.
We've never had that discussion again.