Menen, I am with you - I have come across a few characters who are like you describe!
Some points to consider: Firstly, remember that he is the Captain whether you like it or not and in a lifetime of flying you are bound to come across the odd guy who you don't altogether hit it off with or who appears to be a trfle "unusual" shall we say!
My personal view is that a flight safety issue such as this should not be swept under the carpet. From a pure procedural point of view there is the issue of why he did not deploy speedbrake after the FO had twice called it. From the CRM point of view there is the issue of how he reacted to the FOs operation of the speedbrake and the ramifications this has for flight safety. If you are sitting there as an FO preoccupied with an event like this then you might miss something later which is even more important.
In the first case you have to discuss this man-to-man with the individual concerned. Not in a confrontational way but in a matter of fact, well look we need to work together as a team, I want to be a professional crew member and this event concerns me etc etc. If the individual is not prepared to talk then, assuming you are sure of your facts, it's time to perhaps talk to the training section without even mentioning any names - they probably will have a good idea of who you are talking about anyway!! Just getting it off your chest and some back up that you did do the right thing can often be enough to resolve the issue in your own mind.
In conclusion I don't thinkanything is acheived by not dealing with these issues. If its trivial then take the FIDO approach (Forget It and Drive On!) but from the information you have given I don't think the event you describe is trvial.
Good Luck!