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First, I am going to make the assumption that you want to keep this player in your group.
So here are a couple ideas off the top of my head to help train Fighter Guy.
First idea - Let Fighter Guy be the "Battle God in training", and use the direct violence approach. Just make that approach the non-optimal approach. As an example, there is an evil overlord in the nearby keep/fortress/ city that is preparing to do bad things (summon an army of demons/raise an army of undead/create an army of mutant killer bunnies or whatever). Fighter guy can charge off and attack the troops of the keep/fortress/city, slay them, and then slay the evil overlord. TO give him a good ego boost, have him appointed Lord Protector of the City for a Year. Problems solved ...NOT. The troops were Lawful Neutral types who were only defending the rightful ruler of the keep/fortress/city (the evil overlord over course got to be the ruler through some secret unlawful means, which the PCs could of found and exploted if they used those worthless social skills - this is something to have the other 3 party members do when Fighter Guy is carving up the troops, and have it revealed in order to have an excuss for Fighter Guy to become Lord Protector until the Rightful Lord can take on the job in a year). The troops were also keeping three different groups of Chaotic Evil Clerical insurgents from attacking and killing off the innocent civilians. With the guards gone, there are multiple attacks against the innocents (make sure lots of the innocents are of Fighter Guy's alighnment / Church). Have Clerics of Fighter Guys church come screaming for protection of their flock from the scrounge Fighter Guy has let loose on them. When Fighter Guys finds and kills off one group, have 2 or 3 attacks happen in other parts of the city. Have the population keep reminding him of his failures, not his successes. Eventually, if he doesn't figure it out on his own, have someone explain that Fighter Guy needs to hire/train a city guard. Which should be tough with him not having any of those silly social skills.
Second idea - Have the Fighter Guy's direct approach be necessary, but not sufficient. Set the party up so that are 4 are doing something that must be successfully done for them to succeed in their big mission. For example, give the PCs an artifact destroying mission (a.k.a., LoTRs). Set up the finally so that Fighter Guy is holding off (killing off x per round) an army of Shadow Creatures (being summoned by the artifact), Rogue is removing the traps and opening the locks to the furnance chamber or other special place the artifact is to be destroyed in, Witch is negociating with Spirts etc to keep bad stuff at bay, and Sorcerer / Cleric / Mystic Theurge multiclass is trying to control the artifact to prevent it from summoning more powerfull Shadow creatures. I'd make the Shadow creatures fairly weak individually (not worht a lot of experience points), so that Fighter Guy can kill off say 20 per each that gets a minor hit on him. But there are an infinite supply of them. Eventually Fighter Guy will get a clue that the rest of the four need to succeed before Fighter Guy will be relieved. If you work the timing right, Fighter Guy will have exhausted his supply of healing, his hit points will be getting really low, and he should find if he distracts the other PCs (like by demands one of the other PCs help heal him), his situation gets worst (stronger Shadow Creatures, distracting spirts, locks and traps reclose so it will take longer before the artifact can be disposed of). If all four PCs do their part, they should all be successful. Fighter Guy seems a little dense, so you might have to make it clear to him that could not have completed the mission without the other party members.