I disagree. Let me tell you why.
Firm Captaincy has its place. In this case if safety is not an issue why create conflict. You need the lines of communication open at all times.
If you get on your high horse and slap him down you may close down some of those those lines of communication, when it is not necessary. From then on he may notice some thing amiss that on the surface could be irrelevent to him. If you have been riding him from your high horse he may notice that something amiss and clam up. This is wrong I am aware but it does happen. What we are talking about here is a two manned operation and no place for egos. In an emergency will will need him and every ounce of his help. You wont get the best from him if you have been slapping him down and coming the old madam. Loss of face could mean loss of both of your lives.
Treat him the same if he is a line captain or management.
We all perform best when we are not under stress, so why not try and get the best out of your fellow cockpit member by creating an environment where he can operate to his best. So what he is a nervous flyer? We are all scared to a certain extent, that how we stay alive. A person with no fear will not live long in aviation.
CRM, is very complex and involves a lot of psychology.