If you want students to open up in discussions, you have to build trust. Students respect facilitators who are willing to do what they are asking of participants. Some say facilitators should not participate in the discussion. I argue that facilitators should be intentional, meaningfully participate, and allow themselves to also be vulnerable (and concise), while remaining neutral on participant contributions.
Dynamic discussions begin with setting up norms.
Safe space are indeed important for people to feel comfortable enough to share their perspectives within groups. The focus here is going beyond safe spaces to establish Brave spaces where people not only feel safe to share, but are also brave enough to speak their truth, challenge each other, and have difficult conversations graciously. It is the willingness to be uncomfortable in order to grow in some domain.