Acknowledge that this is a joint learning experience. Ignore the behavior. Redirect question to group or supportive individuals. Recognize participant's feelings and move one. Acknowledge positive points.
Hostility can be a mask for fear.
Reframe hostility as fear to depersonalize it. Respond to fear, not hostility. Remain calm and polite. Keep your temper in check. Don't disagree, but build on or around what has been said.