Couples don't fight about what they think they fight about. It's not "the big five" they identify in surveys: money, sex, raising the kids, in-laws, or house-work. Lovers fight when they believe their partners don't care about how they feel. They fight about the pain of disconnection.
Disconnection occurs most frequently in intimate relationships when fear or anxiety in one causes a sense of inadequacy in the other. There is a survival-based mechanism observed in most social animals, in which fear and anxiety of female members of the pack serve as an automatic alarm system to stimulate aggressive-protective behavior in the males. (The better sense of smell and hearing of females makes them more sensitive to danger and more suited to be social alarms.) When the females get scared, the stronger (and more expendable) males often form a defensive perimeter around the endangered pack.
The human brain is more socially structured than that of any other animal. In us, this primitive interactive mechanism takes on more complicated forms that secretly undermine intimate relationships.
Confronted with the anxiety or fear of a woman, a man typically responds with protection/support. But if he does not know how to protect/support or, more commonly, feels like a failure as a protector, he is likely to turn the aggression onto her (usually in the form of criticism, "superior reasoning," control, etc.) or rein it in by withdrawing in frustration (stonewalling or going quiet). Anger or withdrawal by men often stimulates anxiety or fear of isolation in women, even when his anger or withdrawal has nothing to do with her.
In general, a man is likely to stonewall, be critical, defensive, or contemptuous if he experiences (or, far more commonly, tries to avoid experiencing) feelings of failure or inadequacy as a provider, protector, or lover. A woman is likely to be critical, defensive, or contemptuous if she experiences (or is reminded of having experienced) fear of harm, isolation, or deprivation.
If the couple does not understand this unconscious, interactive dynamic, they will think they have a "communication" problem and will likely continue to provoke anxiety and shame in each other as they try to talk. They will begin to think that they have a bad, insensitive, or selfish partner, and eventually give up on the relationship without understanding the primitive emotional mechanism that did the real damage.
This is particularly tragic, because the fear-shame interaction is not the result of one party doing something to the other. It happens to them simultaneously. If they do not blame it on each other, they can work together to disarm what is really primitive, pre-verbal dynamic.
First they must train themselves to remember that they care about each other when they disagree.