Obstacles to Discussion in the classroom

http://www.theideacenter.org/sites/default/files/IDEA_Paper_49.pdf
The above paper, by William B Cashin, provides a pretty basic overview of the use of discussion in the classroom, but one part that stood out for me was the notion of obstacles in discussion. Not because the obstacles they posit are particularly new or unexpected but I was thinking that it might be useful to actually bring these up with the class and use them as a discussion topic: to quote from the article:

"First, what are some obstacles to student participation?
Svinicki and McKeachie (2011, pp. 44-45) discuss five
barriers to good discussion: habits of passive learning; fear
of appearing stupid; trying too hard to find the answer the
teacher is looking for; failing to see value in the discussion
topic or process; and wanting to settle on a solution before
alternatives have been considered."

Another point he makes is ensuring students that the purpose of the discussion is to develop the "best" answer, not to prove you are right.