Well, the approach we take to customers who are angry in my business is much the same, since we don't want our customer to be angry if there's a way to avoid it.As a business, if a customer was abusive. You review the events that lead up to the issue at hand. If a resolution can't be found, explain why it can't be found. This is the approach I take with my business.
The main difference to yours is that the MOMENT they become abusive, their reasons cease to matter even in the slightest and we cut the relationship off immediately.