Jorge - comment overall is best left to the company enquiry. I think you have acted correctly in reporting the matter as you have. Not a pleasant experience.
I assume you have had time to read the 'rules' on Captain's Discretion'? In the UK, the Captain has the authority to extend duty time within the UK limits. It may or may not be the same in your area. In that case he would have been correct in exercising his sole authority to make the decision, having taken into account the fitness of the crew to operate the extended duty. I assume the 20% extension is what your rules lay down?
The part which is of concern is, as you say, the manner in which your Captain acted. This would appear to need addressing by the company. If you are caught in a company 'old boys' club' then there is not much you can do. If you are a member of a pilots' association, speak to them.
Out of interest, what was your position/role on the flight deck? If 3 crew are required for the operation then there is another potential problem in what you describe as happening. What was the response of the other co-pilot and was he/she in a fit state to operate following those events you describe?