We deal with it ALL of the time. Daily! It's part of the game. People generally don't like change. Hiring managers are people. They too don't like change when wearing their hiring manager hat. You deal with it. Behavioral or compentency based interviewing typically garners better hires because you are digging deeper. If they can't get that and don't want to change, none of us can force a hiring manager to do what we request of them, until the turnover gets so bad that either their job is in jeopardy or they cry uncle and buck up to best practice hiring processes.
I've been at this a long time. Push back is part of the game. Once you establish crediblity with a hiring manger and you have successes with them the push back usually stops and they worship the ground you walk on. Well some of the time!
Are you new in your role? That might be why you have push back, or the hiring manager is new to the company and of course, they always know more than you do because recruiting is "so easy"........right!