While not an exact fit (because it doesn't necessarily involve figures of authority), what about the following:

If they don't practice what they preach why should we?

from def:

To do the things that you advise other people to do:

 

He's such a hypocrite! He never practises what he preaches.

(Cambridge)

Also, while not an idiom, hypocrite fits as well.

While not an exact fit (because it doesn't necessarily involve figures of authority), what about the following:

If they don't practice what they preach why should we?

from def:

To do the things that you advise other people to do:

He's such a hypocrite! He never practises what he preaches.

(Cambridge)

Also, while not an idiom, hypocrite fits as well.

While not an exact fit (Doesn't necessarily involve figures of authority) what about the following;

If they don't practice what they preach why should we?

from def;

To do the things that you advise other people to do:

He's such a hypocrite! He never practises what he preaches.

(Cambridge)

Also, while not an idiom, hypocrite fits as well.

While not an exact fit (because it doesn't necessarily involve figures of authority), what about the following:

If they don't practice what they preach why should we?

from def:

To do the things that you advise other people to do:

He's such a hypocrite! He never practises what he preaches.

(Cambridge)

Also, while not an idiom, hypocrite fits as well.