does this through violence and force, in an anarchic “tearing down” of the current state of affairs in order to make way for the new. Just as he and his cult are attempting to destroy what they think doesn’t work in the current society, Tyler is attempting to tear down the parts of himself he doesn’t approve of. He goes way too far, but his actions are a reaction to the timid, repressed, subservient life the narrator has come to live. Through violence, he is trying to remove his barriers and remove ingrained social niceties that don’t serve a productive purpose.

Ironically, he’s trying to do all this by engaging in a hyper-masculine activity. Some of Tyler Durden’s speech and actions reflect toxically masculine beliefs—for example, that this repression is due to feminization (and not, say, capitalist power structures and social conditioning). In some ways he not only goes too far but is also reacting to the wrong thing. This is where I believe the book’s satire comes into play, as these men blame femininity and women (see: Marla’s portrayal in the narrator's eyes throughout much of the book) instead of the very obvious class disparity that had put them in this situation. Because, yes, they do engage in anarchist, anti-capitalist activities, but their fighting and much of their language is an attempt to restore traditional masculinity over women and femininity.

Violence is a significant part of the theme of masculinity that dominates Fight Club.

Violence can fit into several of the novel's themes. However, the novel's theme of asserting masculinity is directly linked to violence.  For the men who participate in fight club, violence is the path to reclaim their identity. When they fight, it is a rejection of the social expectation that has taken away from masculine identity. The perceived domestication of men is subverted through violence. Violence is the only way to undermine the inauthenticity of conventional society:  “...who you are at fight club was not who you are in the real world.”  Violence supplants the socially tranquil image of masculinity.  It tears this mask off and enables men to embrace a primally true nature. Violence in the form of hand to hand fighting, without weapons or even shirts, is a significant part of this reclamation.  

The novel's theme of reclaiming male identity suggests that violence can help to find truth.  Violence is a way for men to "lose everything" so that they can then gain "everything." Tyler suggests that he is "breaking attachment to physical power and possessions," and that violence is critical in this process because only through destruction of self is he able to "discover the greater power" of his spirit.  Such an idea reflects how violence is a significant part of the novel's theme of reclaiming male identity.

I apologize for the generalities of my answer at the expense of a specific response to your question.  My mistake.

The fighting in Fight Club is clearly intended as an outlet for the narrator to express his masculinity through an activity traditionally associated with machismo, or the display of virility or manliness.  As pointed out in my previous answer, the narrator, "Joe," is experiencing a crisis of confidence.  He is disillusioned regarding his professional and personal status.  His job provides no satisfaction, and his inability to sleep at night undermines his mental well-being.  He conjures up a friend, Tyler, who serves as an alter ego, providing the path to a more virile masculinity through the use of carefully structured fighting intended to provide an outlet for pent-up testosterone.  The attractiveness of Fight Club to its growing number of members is the regulated nature of the violence; in effect, they can engage in what used to be referred to as "the manly art of self-defense" through "fisticuffs."  A real-life London, England, organization sponsors a "Being a Man" festival, promoting the opportunity for men to "take part in only the manliest of pursuits: punching another man in the face until his teeth rattle around like Tic Tacs." [See www.now-here-this.timeout.com]  In Fight Club, violence is associated with masculinity, as it has throughout human history.

Chuck Palahniuk, in his novel Fight Club, addresses the issue of masculinity in a manner that is both blatant and circuitous at the same time.  The novel’s narrator, whose alter-ego would be established with the creation of Tyler Durden, is a man ill-at-ease with his place in contemporary society.  Suffering from insomnia, and after repeated visits to his doctor, the narrator’s physician recommends he begin to attend therapy sessions for patients of seriously debilitating diseases so that he can learn to empathize with real suffering.  As Palahniuk’s narrator – presumably named Joe, hinted at by his references to his own anatomy, as with the statement, “I’m Joe’s Clenching Bowels” – describes the physician’s prescription:

“My doctor said, if I wanted to see real pain, I should swing by First Eucharist on a Tuesday night. See the brain parasites. See the degenerative bone diseases. The organic brain dysfunctions. See the cancer patients getting by.”

This explains the scene early in the novel when the narrator is engaged in a surrealistic exchange involving physical struggle with the much larger and physically-stronger “Bob,” who is suffering from testicular cancer:

“Bob cries because six months ago, his testicles were removed. Then hormone support therapy. Bob has tits because his testosterone ration is too high. Raise the testosterone level too much, your body ups the estrogen to seek a balance.”

The implication is clear: loss of the male genitalia has enabled men to express their emotions in a way that would otherwise be unmanly.  The themes of crying and testicular cancer play a large role in the opening of Palahniuk’s book, and set the stage for the introduction of Tyler, the anti-narrator who opens the narrator’s eyes to the exhilarating worlds of violence and disobedience.  Tyler represents everything the narrator is not, as illustrated in the following passage in which the narrator provides a self-description:

“In the real world, I'm a recall campaign coordinator in a shirt and tie, sitting in the dark with a mouthful of blood and changing the overheads and slides as my boss tells Microsoft how he chose a particular shade of pale cornflower blue for an icon.”

The narrator, or “Joe,” is a self-loathing automaton who clearly yearns for more meaningful pursuits than his job provides, and the creation of Tyler provides just such an opportunity to break away, at least for a while, from the dehumanizing and gender-neutral world in which he is otherwise immersed.

The role of masculinity is further developed with the novel’s transition to anti-consumerism.  For the narrator, already suffering from a serious identify crisis, the accumulation of material possessions substitutes for a more meaningful spiritual identity.  Again, it is through Tyler that the narrator begins to understand the linkage between consumerism and masculinity, and about the need to divest oneself of material goods in order to achieve a spiritual breakthrough:

"I'm breaking my attachment to physical power and possessions,' Tyler whispered, "because only through destroying myself can I discover the greater power of my spirit."

The relationship between “Joe” and Tyler is imaginary, of course.  Tyler is a figment of “Joe’s” imagination, and exists to provide a much-needed outlet for the latter’s pent-up frustrations regarding his diminishing masculinity.  Even the character of Marla Singer seems to exist solely for the purpose of challenging “Joe’s” masculinity and representing his feminine side.  In a crucial scene in a diner, a waiter refers to “the lady” when addressing “Joe/Marla” yet, if “Marla” is a figment of “Joe’s” imagination, then is the exchange with the waiter another way in which Palahniuk addresses the issue of Joe’s masculinity?  As “Joe and Marla” discuss identity, the former makes a suggestion to the latter that resurrects the theme of genitalia discussed earlier:

“From now on, I tell Marla, she has to follow me everywhere at night, and write down everywhere I go. Who do I see. Do I castrate anyone important. That sort of detail.”

Masculinity is a dominant theme in Fight Club.  Anyone well-briefed on the gutter-mentality that emerges in a testosterone-fueled environment can’t miss the significance of the discussion of “clams” and “clam chowder” during that scene at the diner, during which the waiter appears to deride “Joe’s” masculinity.  Not subtle, but certainly subject to interpretation.