In light of the rather odd juxtaposition of the confirmation hearings on one hand and some vociferous divisions between Catholics I respect on the other, I thought it might be useful to offer a word or two on the notion of Catholicism as society. One tremendous advantage of Zubirian thought, an advantage noted by Ignacio Ellacuria among others, is that it provides a meaningful metaphysical account of society. Indeed, Zubiri's entire picture of the Church as Body of Christ is based on the societal interrelation of members living the life of Christ both individually and collectively. You can never separate the individual from the social in being molded to the Trinitarian life.
Part of that realization is to perceive that one can never have "the Catholic faith" as an isolated individual. The individual's faith can never be defined apart from the societal faith, because the individual can never be defined apart from his own historicity and social setting, creating a constant dialogue within the Church. Indeed, Catholicism is in some sense a discussion among Catholics about what Catholicism is; that is an essential part of the metaphysical constitution of the Church. There is no "argument for" Catholicism, because Catholicism is not a subjective belief; rather, it is an objective reality. It is the objective reality, not one's own imperfect perception of the reality, that is the ground of unity. At the same time, it is the conviction of sharing an objective reality that makes the subjective views meaningful; knowing that we Catholics have the shared reality is what gives us optimism in dialogue that something good will come of the discussion.
Part of the problem is in the apologetic emphasis on the divisiveness of Protestantism, acting as if Catholicism is better because its principle of doctrinal authority ensures doctrinal uniformity. In fact, the case is quite the opposite. It is the conviction that there is one faith, and that this faith is realized in the Catholic Church, that brings Catholics together in dialogue to overcome differences. In Protestantism, there is no incentive to do so, because there is no metaphysical imperative to realize unity in a real way. Either the importance of the disagreement is minimized by calling the matter "unessential," or there is schism, or there is simply mutual monologue. Only in Catholicism is dialogue an essential part of the process, because only there is the innate conviction that there is a goal in sight and that greater unity can be attained.
ISTM that suppression of this dialogue is where Catholicism has suffered its greatest losses. I think my bishop's response to the sexual abuse scandals using the theme "Breaking the Silence" makes a great deal of sense. As a matter of practice, the Pope has never been able to suppress dialogue unilaterally, because even his pronouncements have simply sparked more dialogue. And the use of force and political power has historically proved equally futile, producing the moments of greatest shame in the Church's history. Ultimately, it is contrary to the nature of Catholicism, which preserves the faith in a historically submerged dialogue between past and present. Voices are not silenced in Catholicism, and efforts to do so, whether by liberalism or rigorous traditionalism, have failed. This is why the nouvelle theologie succeeded so powerfully with ressourcement; the voices of Tradition could not be silenced by any amount of rationalistic speculation.
That's not to say that "dissent" ought to be unlimited; obviously, there comes a point at which one is no longer committed to the real Church and bringing the ideal into the world. That can take the form of pure idealism (disregarding the "real world" in one's theology) or outright denial of what the Church has to say (no longer sincerely trying to listen to the voice of the Tradition). But most of the time, fear of dissent is simply fear of dialogue, fear of the human process, fear of our own finitude. My reply would simply be that one need not fear finitude if one has faith in the objective reality of God making dialogue possible, and if one doubts this, one wonders how strong one's Catholic faith truly is.
UPDATE -- Newlywed Tim Enloe linking this post actually reminded me of a useful analogy. Fr. Al Kimel's post "Do We Marry the Right Person?" emphasizes the sheer impossibility of making an argument for the objective state of marriage. Marriage is not a belief about marriage, so although people who aren't Britney Spears ordinarily have reasons for getting married (which may be different between the spouses), no argument makes one married! There is no syllogistic set of premises reaching a state of belief equivalent to the state of being married. Furthermore, there is no concrete concept of marriage apart from actually being married, and neither spouse's belief about marriage determines what the marriage will be. Asking what the "argument for" Catholicism is, is akin to asking what the "argument for" getting married is. One might have reasons, but you'd be deluding yourself to think that there was an argument that compelled marriage, just as you'd be deluding yourself to think that there is an "argument for" Catholicism. Conversely, there is no argument against being Catholic that can be made apart from the individual Catholic. Attempting to make an "argument for" Catholicism simply misses that Catholicism is not a cognitive state, any more than marriage is a cognitive state. You're consenting to a real relationship that will define your beliefs, not a real belief about a relationship.