Destructive Forces in Christianity. . .

1.  The reduction of Christianity to morality has been one of the most potent forces for the destruction of the faith.  Liberals emptied the faith of its factual base, undermining the truthfulness of Scripture, the accuracy of the Jesus proclaimed through the ages, and the need for redemption from sin.  With a Jesus divorced from history and a Bible devoid of fact, morality is all that is left.  The liberals insisted that this was not simply all that was left but the essence and core of Christian revelation.  Those conservative Protestants who protested this liberalism ended up also reducing faith to morality because of their behavioral standards.  Though they used a distinctly different compass than the liberals, they nonetheless charted the vitality of the faith by the righteousness of the adherents. 
2. The rise of how-to Christianity has reduced Christianity to a mere assist to the dreams, hopes, and aspirations of mankind.  The heart is left unredeemed and the goals unchallenged so that the only thing left is the methodology -- how to achieve them.  The focus remains on the Christian, assuring that he or she can learn to become a better person, live a better life, achieve more satisfaction, enjoy a better job, etc...  Salvation is that which enables the person to reach their dreams -- a mere technique or enlightenment that enables the person to change their ways.  It is somewhat gnostic except that the secret path is less spiritual than practical.
3. Confusion of introspection with spirituality.  Navel gazing Christianity has led to second guessing nearly everything doctrinal through the lens of self as well as divorcing spirituality from Spirit.  The questions of life are met not by divine wisdom or revelation but by getting in touch with one's own feelings, wants, and desires.  The doubts about whether or not the person is getting all that could be gotten from faith, worship, prayer, etc... have led to a vagabond Christianity in which the seeker is always on the path of seeking, switching faiths and churches and guide books as regularly as clockwork.
4. The rise of the social gospel in which every problem becomes a cause and the redemptive work of the Kingdom to community organization has given us a local purpose but without much of a transcendent need or purpose.  Advocacy has become the holy sacrament of the social gospel and whether or not the cause of injustice, acceptance gay and lesbian marriage/rights, nature, or the poor, the pursuit of a strident righteousness of the position seems to be the piety of this sacrament.  It is essential legalism and coercion is an acceptable means to achieve the goal, enacting, and enforcing the ways and will of God on behalf of the cause.  It is not a stretch to see how this can turn into either an intense patriotism or the self-loathing of a people who cannot atone too much for their sins.  The desire for a theocracy in which one does not have to depend upon the individual conscience but can achieve the ends through the more efficient means of governmental intervention and law tends to devalue personal conversion.

To name but a few. . .