This is similar to what I struggled with early in my consulting career. As a consultant (telling the client what to do, not a contractor, where they tell me what to do) I often told them to do A and they wanted to do B. Initially this made me crazed and hard to work with (at least.)
However, I eventually became enlightened (small "e") and developed what I called my "Consultant 2 step."
Me: You should do A and here is why...
Them: we want to do B
Me: OK, but if you do, this is what will happen . So, you should do A, and here is why (again).
Them: We want to do B.
Me: OK.
I realized "it's not my system and not my project."
and
Life goes on.
and,from the Tao De Jing:
57. Conquer with Inaction
Do not control the people with laws,
Nor violence nor espionage,
But conquer them with inaction.
For:
The more morals and taboos there are,
The more cruelty afflicts people;
The more guns and knives there are,
The more factions divide people;
The more arts and skills there are,
The more change obsoletes people;
The more laws and taxes there are,
The more theft corrupts people.
Yet take no action, and the people nurture each other;
Make no laws, and the people deal fairly with each other;
Own no interest, and the people cooperate with each other;
Express no desire, and the people harmonize with eachother.