As facilitator, the coach is responsible for helping to make the discussion run smoothly, occasionally identifying and remedying team behavior the impedes the team’s performance.
As facilitator, you should communicate to members that all ideas are welcome.
Clarify poorly worded ideas for the group. When someone gets off track, you should prevent discussion of the irrelevant issues without discouraging the member who made the remarks.
Your goal is to get participation from all, which means encouraging quieter members to talk while discouraging domination by others.
Incidentally, if you can share this facilitation role with team members, providing team member with facilitation training prior to start-up, you will take some of the pressure off yourself for ensuring an open communication climate. The group as a whole may work together to create a positive, collaborative environment for problem discussion and resolution.