Chang makes the least amount of sense when you put a little thought into it. Some guy who's civilization is dying and hates the Federation... conspires to kill his civilization by teaming with the Federation?
I think the only reason people like to remember Chang is that he was well-acted and thats it. He wasn't a particularly menacing villian.
I couldn't disagree more. If you remember at the beginning of the movie they mention certain elements that would rather seek a military solution and "die fighting."
Plus the Klingon mentality places a high value on death in battle. Peace for the Klingons means accepting another group as equals something they don't seem to like doing. As Martok said, "We do not embrace other cultures we conquer them."
Chang seemed to view peace with the Federation as admitting defeat, or worse. He'd rather die fighting a hopeless battle for his people's way of life rather then submit to a peaceful solution that could run the risk of destroying their culture and way of life.
To really understand Chang you'd have to look at his situation... while this is a crude analogy, put yourself in say in the shoes of a Soviet soldier at the end of the Cold war. You've been fed all kinds of propaganda by your government. You've been bread, raised, and trained in the belief that some day you would wage glorious battle against your democratic enemies in the name of the mother land. Suddenly, your country goes bankrupt and starts accepting aid from the former enemy.
Suddenly your way of life is over. Your military machine is being broken down due to treaties signed with your new "ally" and your weapons are being sold to the highest bidder. You as a loyal red army soldier can do little but stand there watching your way of life disappear as the entire country is being reformed with the help of someone you were trained to kill.
Watching all this happening with the sounds of Glory and honor ringing in your ear. A soldier deranged on such ideals may find comfort in a small radical group that plans on taking one final stab at the enemy to the west in the name of the motherland.