Trubru....like yourself, I consider myself to be an easy going captain who actively encourages constant communication on the flight deck. I always make it clear to a new FO before a flight that we are there as a team in order to conduct a safe and expeditious flight, however, as commander, the full responsibility for the safety of the a/c and its passengers lies with me. I ensure that if he/she has any concerns during the flight, that they must speak up. That includes any reservations they may have on any of my actions. If I've made a mistake (and gods knows there have been a few!), I'll immediatly holds my hands up and apologise, and I'd expect them to do the same.
In my experience, one of the main problems with over-confidence is that it onsets complacency, which, as we all know, can lead to tragedy. Thankfully, I haven't flown with too many over-confident FO's in the past. However the ones that I have flown with, I found myself nipping it in the bud pretty much straight away in such a way that they realise it's not a character assassination, but purely a professional debrief in the interests of flight safety and good CRM. Otherwise I'd end up with a situation such as yours (i.e - an constant atmosphere in the cockpit which demoralises everyone).
In my opinion I believe you should have a serious chat with your FO, reminding him that you are the Captain of the A/C and as such you are responsible for it's complete safety and that of your passengers - even for his mistakes. Remind him that if anything had gone wrong during the landing roll at that game reserve, it would have been your head on the line. Maybe I'm wrong, but reading between the lines, their seems to be a serious lack of respect here. Ultimately, you need to sort it out sooner rather than later otherwise you're going to end up despising the guy and ironically criticising and nit-picking everything he does.