I have usually found, after nearly thirty years in command of heavy jet transports that the following works wonders....
'I am in command of the aircraft and I operate according to the laid down company policy. If, for some reason, you do not agree, the Fleet Manager is only a phone call away.'
This has worked every time.
I have not, nor will I put up with caustic comments from the RH seat...period.
In that 30 year period, only one First Officer complained to the fleet manager, and in this one case only, the concerned individual was de-moted to a lower fleet.
The fleet manager couldn't stand him either, apparently.