Sure, but if people are using the retro as a vent session, maybe it's because they need an outlet. Perhaps a separate meeting titled "vent session" is what you want. Although it's important to have action come out of that meeting as well, don't want to just channels peoples' real concerns into a meeting that is intended to hear them out and then do nothing. Manipulating peoples' concerns into a channel where they are made unobstructive and ineffective, so they can be easier ignored is a pattern of bad-faith bosses. Conflict avoidance is toxic. You and the team building skills in conflict resolution can help.