I totally disagree. It is our job to teach multiple points of view. And to be honest almost all history textbooks are extremely biased towards WASP viewpoints (aka the "winners" of history). That is why I use Howard Zinn in my classroom to show the other side (but of course not exclusively). My other argument is that every person, every source, and yes every teacher is biased. Therefore just by the materials the teacher selects she is making a biased decision. The best option is to give multiple sources from multiple viewpoints and PBL takes it one step further by encouraging students to go out and research and find these different views.
The problem with student research sometimes is that it too is biased. Students often lack the historical background to start their research and identify different viewpoints. My approach to this is that during "work time" I give them specific articles, primary sources, etc to steer them into interesting questions and alternative viewpoints for their topic. Then I encourage them to continue to research on the topic and go deeper. Then we come back in a class discussion or Socratic circle and they can discuss different aspects of it.
Case in point is the 9/11 project we are currently working on where students will design a monument commemorating that time period. Students immediately gravitated toward the American victims/heroes side of history. But our driving question was "Why did 9/11 happen and how should we respond to terrorism?"
We read Ender's Game and used the concept of "Speaker for the Dead" to shift students to think of 9/11 and the following wars in Afghanistan and Iraq from a Middle Eastern perspective. After researching all of the American Interventions since the end of the Cold War students were able to see (but not justify) the motives of terrorism. Looking at the events post 9/11 such as the civilian casualties in the wars, Abu Graib, Guantanamo Bay, and abuses of the Patriot Act students were also critical of many of our responses to 9/11. Now students are designing much more complex monuments that are not just American "hero worship" but actual critiques of history.
In reality I believe we do our students an injustice if we do NOT ask them to be empathetic and look at history from the viewpoint of its "losers"-the weak, the down trodden, the humble citizens who are just trying to raise their families and live the best they know how. Because that is ultimately the category that most humans (including myself) fall into as few of us will ever be famous or huge centers of power. I also think most of the greatest