I disagree with #6. Writing an argumenative paper and presenting both sides most often creates a weak paper. As far as bias goes, like most posts have stated, your teacher is probably warning you not to include a personal opinion. By nature of argument, you are going to be bias toward one side. This does not, however, need to become an emotional bias, nor a "racist" type of bias.
Avoid using any kind of emotional language and certainly deny yourself the right to include your own opinion. Report facts, statistics, and quotes from other scholarly sources, and analyze the information objectively. If you are against religious fundamentalism, show actual cases where it has endangered society, or specific groups of people.
You can show your disagreement with religious fundamentalism without coming right out and saying, "These people are nuts!" Does that make sense?