In your answer, emphasize that you understand that being professional is key in such situations but there are also safety and common courtesy issues at play too. You can still be professional without agreeing to be someone's verbal punching bag.

"I understand that people can have a variety of emotions during a case. Ideally, the attorney can provide advanced notice if they expect the client will be calling or coming in who may be upset. It is always easier to prepare for the interaction if you are expecting it. Otherwise, if I am talking with an angry client, I do my best to mitigate the situation and show compassion. It is only when they move past the emotion that they will better understand the issue or outcome at hand. Those situations are never fun but so far I have been able to handle upset clients without incident."