Quite agree with 411a, when I first got my command one of my biggest worries was that I had little experience in supervising and monitoring someone elses flying which in effect is what you are doing when you are PNF and the Captain. It turned out to not really be a problem as the huge majority of FOs in the company are very able and very easy to work with.
As an FO I used to dislike skippers who would give you the leg and then spend the whole time telling you what to do. I used to think "well why don't you fly it and I will do the radio". I make a real effort not to picky about the other guys operation and when I do need to say something to do it as diplomatically as possible. I also realise that it is much harder for the FO to say something to me and try to foster the sort of flightdeck atmosphere where they find it easy to do so. I think you will find that the majority of guys who hassle and interfere with FO's are little under confident of thier own abilities and as you said are not that special themselves, it's just thier way of coping with it.
BUT, at the end of the day the guy in the left seat is in charge and the guy in the right seat is not and there are times when you just have to bite your lip and get on with it despite what your feelings are. A saying I often hear at work is "if everyone was the same it would be boring", unless things are getting unsafe I would just let it wash over you, the next day you will probably fly with someone else anyway.
Eventually you will be in a position to set the tone for the day and it's very nice to be able to do that, you may find however that from the left seat things are not quite as black and white as they sometimes appear from the right.