Numerous others have already responded to the declaration, so there's little need for me to go into detail about many of the document's more glaring absurdities: the persecution complex that causes conservative evangelicals to view every disagreement as a sign that concentration camps lurk just around the next bend; the narcissistic self-comparisons to great historical leaders who really did face persecution; the assumption that no good Christian could possibly disagree with any of their dogmatic claims; the conspiracy theories that thinly mask their animosity toward any gay person audacious enough to demand to be treated as an equal; the thoroughly unbiblical notion that the church's role in society is to rule over nonbelievers for their own good.
Such an emphasis also places the church at odds with Jesus, who called on his followers to leave family and familial obligations behind to follow him, and who warned that families would divide over him. And it does little better by the Apostle Paul, an unmarried man who described marriage as a concession to those too weak to handle celibacy, and who declared that there was no male or female in the Kingdom of God.
I am leery of declaring that I have God pinned down so well that I can speak on his behalf. But it would be logical to assume that, if the Bible is a reliable source of information on God, that one could get a sense of his priorities based on the amount of space that the biblical authors devote to different topics. Based on that assumption, the following priorities would seem to be at or close to the top of the list.
(I am omitting the concept of holiness from this list, since that term has become conflated with sexual purity and heterosexuality, even though holiness, at its root, is simply about being "set apart" - a concept that goes far beyond the sin avoidance that consumes the attention of most evangelicals. I would also argue that holiness cannot be properly understood without taking into account all of the biblical priorities I list below.)
Justice. Justice is a broad concept that can be applied both to legal matters and personal situations, but at its most basic one can understand what is just through application of the Golden Rule (a concept most commonly attributed to the teachings of Christ, though many of its truest adherents follow other belief systems). If you would not want to be treated the way you are treating another person, then you are acting unjustly.
Unfortunately fundamentalistic thought has twisted application of the Golden Rule, since individuals driven by a fear of being cast into hell by an easily offended god logically consider any action taken (no matter how abusive) to save another person from eternal damnation to be loving and just. And indeed, the authors of the Manhattan Declaration no doubt consider themselves striving to save souls when they lobby to politically and socially oppress gays and other sexual minorities. In reality, though, if some future majority were to persecute them in similar ways "for their own good," not one of the declaration's signers would consider it just.
Humility. This is another concept that must be rescued from fundamentalistic thinking. To the fundamentalist, being humble is all about obedience, as understood by their own interpretation of the Bible. Since, by this definition, anyone who disagrees with their interpretation is not humble, it becomes entirely appropriate for them to look down on (and even persecute) such dissenters. That the resulting superiority complex is the very antithesis of humility never even occurs to them.
Likewise, the authors of the Manhattan Declaration are quite proud of their own self-proclaimed humility. From the opening of the document they waste no time establishing themselves as the sole brave defenders of Western Civilization and every single thing that is good in the world, and pile on the self-comparisons to leaders representing nearly every great social movement in history. Again, the irony is completely lost on them.
Compassion/Charity/Hospitality. Numerous actions fall under this category, including helping the poor, providing for widows and orphans, welcoming strangers, tending to the sick, showing mercy, etc. One would have to discard most of the Gospels - and much of the Prophets and Epistles - to avoid the commands related to this concept. Throughout church history, countless Christian endeavors have been launched toward these ends over the centuries, and such selfless charity was one of the qualities that drew early converts to the faith.
Such concerns seem to be secondary to the authors of the Manhattan Declaration, however. Throughout their manifesto, charity gets attention only through the lens of the nuclear family, and even then seems more to be a byproduct of marital procreation than a mandate that captured more of Jesus' attention than any other subject. Certainly no compassion can be spared for those the declaration views as enemies of God and destroyers of civilization, except within the same hell-centric paradigm through which its authors redefine justice.
Idolatry. If I were to single out one theme as the most important of all, it would be idolatry. No other subject receives as much attention in the Bible, and many other concerns intertwine with it. Anything that a person gives priority over God constitutes an idol. Even an otherwise good thing can become an idol when too much value is placed upon it. The doctrine of inerrancy is a perfect example of this, as it elevates the Bible to the status of a comprehensive rulebook free of even the slightest error (a claim never found in the Bible itself - God alone merits being described as perfect), and the only source through which God can reliably communicate with his people. With an inerrant Bible in hand, a believer need never wrestle with the doubts that drive us to press further into relationship with God.
The pedestal on which many evangelicals have placed marriage and family is another example. By elevating an institution that validates their feelings and brings them personal happiness above priorities that receive far more attention in the Bible (and this from inerrantists, no less), the authors and signers of the Manhattan Declaration conflate their own will with God's, thereby completing the very usurpation of divine authority that they accuse their "liberal" brothers and sisters of.
It would be easy to give into the notion that one could do some good by pointing these things out to the declaration's supporters, but few of them are ever likely to see the false god they have created for what it is, steeped as they are in the all-too-human notion that the infinite Creator of the universe and the Author of unfathomable wonders is small enough to be contained in a book and petty enough to share all of their likes and dislikes. Such is the tragedy of the fundamentalist mindset. And such is the legacy that created the Manhattan Declaration.