It's important not to get hung up arguing about or debating the validity of excuses. Every BDPAer makes excuses at one time or another. It's better to ignore the excuse, and focus on the job at hand.
For instance, a BDPA volunteer tells you that he "would have finished the job but people kept interrupting me."
Wrong Answer: "Why did you let them interrupt you? And, by the way, who was interrupting you?"The right answer keeps the discussion focused on the job, not the excuse. As a general rule, attack the problem and ignore the excuse.
Right Answer: "Fine. What is the status of the job now, and when will you be finished?"