This "in-class" pressure can actually speak to advantages of asynchronous discussions in the online environment, where that level of self-conscious interaction can be taken out of the equation.
"Huitt, W. (2007). Maslow's hierarchy of needs. Educational Psychology Interactive. Valdosta, GA: Valdosta State University. Retrieved [date] from, http://www.edpsycinteractive.org/topics/regsys/maslow.html"
This would also be important from an efficient instructional design perspective. You would need to align the course objectives with the specific discussion questions, and how they are crafted, (ie. what level of Bloom's Taxonomy, etc.)