How you respond to an upset parent can make or break the relationship you have with the family. Here's some practical steps from Harvard Business Review about being a good listener when someone is in "spew" mode.
Ask them what they are most frustrated about. Then let them vent their feelings. As they vent, listen for words that have a lot of emotion attached to them. Words like "never" or "didn't" or "screwed up." Listen for words they say with high inflection.
Ask them to explain more about what they mean by the word(s) that had a lot of emotion attached to them. This will help them release their anger even more.
Then ask them what they are most angry about. This continues to let them release their angry emotions. During this time, you may feel your own emotions amping up, put don't give in to the urge to jump into a debate. Listen without interrupting. Let them have their say and get everything off their chest.
Next, ask them what they are really worried about. After they have shared, ask them again to tell you more about their worry. This will allow you to get to the core of their emotional wound.
Finally, say, "Now I know why you are so frustrated, angry, and worried. Since we can't turn time back, let's put our heads together and come up with a solution."
Just remember, when a parent gets upset, what you tell them is less important than what you enable them to tell you. After they share their frustrations, angers, and worries, then you are ready to move into a healthy conversation and resolution.