Teachings of Christ
As understood by most people, the teachings of Christ and their interpretation by his disciples in letters and prophesies are known as the "New testament". These writings are respected by several of the major religions, including Islam and parts of Judaism who interpret the teachings they contain as words of a prophet.
The teachings of Christ were used as the basis for the foundation of the institution now known as the Roman Catholic church. In the eyes of its adherents, there is an unbroken line from them to the appointment of Paul as Jesus' disciple. Those who are outside this institution have no access to God, save by coming into the institution.
There are, however, other institutions that also claim unique access to God. Some of these follow the teachings of Christ. Some of those only align themselves with people who do also. Others align themselves only with those who are accepted within their institution. Others still align themselves with groups that are opposed to in belief and/or action to the teachings of Jesus.
A major and highly motivated example, though in some ways very weak as they are easy to manipulate, is the southern baptist church prevalent in the Southern states of the US. These groups have been successfully controlled and made loyal with limited agenda campaigning that neglects most issues and picks up a small number of highly emotive but financially irrelevant ones that are offensive to other political parties, such as abortion, euthanasia, publicly funded works of art, gay marriage and the display of the ten commandments in public buildings.
Further, due to this political base, and the embedded presence required to drive opinion, there are activists within the churches who do not follow Christ's teachings any more than is necessary to convince others. They don't believe in the causes pursued as the minor inconvenience they cause to them are outweighed by the financial gains (through share value, tax exemption, etc)
They often stay out of the limelight, but whisper advice to those in prominence who may well actually believe. These people and those who follow their teachings, often contradictory to Jesus' except perhaps in a Pharisaical way, are known as Christers, Christists or Christianists.
This classification is distinct from, although it overlaps with, Fundamentalist Christians who typically interpret the bible literally, often including the book of Genesis, the one that describes the creation of the world. Such people are rarely rational, although some believe that they are due to their (sometimes very strong) grasp of limited aspects of the logical mechanisms of the use of language to reason.
This makes them much easier to control in the way described above. This is because their core beliefs originate in raw, often unjustified or misdirected, emotion, which then shapes their views, rather than seeking out the truth of events, then allowing that knowledge to shape their emotions.
Due to their high motivation and ease of their manipulation, they can be employed for effective campaigns of "flak" against media outlets that broadcast politically unacceptable views. These can be highly inconsistent in their justification for the reasons outlined above.
Historically, appeals were made to anti-communist sentiment, associating the fear of communist invasion or attack with anything that could be vaguely interpreted as left-wing, and associating all moral corruption in society with left-wing values, rather than, say, the political and sociological influence of the priests of Mammon, the god of money, in the US.
Other Christians recognise the value of institutions and tradition, but consider it distinct from the Church of Christ, which they believe to be a body of people within and without those institutions that follow the will of Christ, ask him to forgive what they've done against those teachings and let him change them (this is called accepting his forgiveness). Their relationship is with God and their brothers and sisters in Christ, not with a church or any other human-owned intermediary.
Further, many question the absolute nature of many aspects of the teachings and suggest that they are contextual. This position is, in fact, implicitly accepted but almost never acknowledged: few denominations require women to cover their heads in church, for instance.