How do you pacify an irate customer?

Let them vent and understand their frustrations. Help them understand that you're there to help them, don't get frustrated with their attitude because most of the time they're not focused on the way their acting and will judge you the first opportunity they get. Reassure them that you're dedicated to helping them, and try to relate to their problem as much as you can. Have a lot of dialog, this will help them realize you're with them, and not against them.