the bath and the bucket story (lateral thinking, making assumptions, dangers of judging people)

Given the title (on the subject of buckets..) and its quick simple message.
The story illustrates lateral thinking, narrow-mindedness, the risks of making assumptions, and judging people and situations:

A party of suppliers was being given a tour of a mental hospital.
One of the visitors had made some very insulting remarks about the patients.
After the tour the visitors were introduced to various members of staff in the canteen.
The rude visitor chatted to one of the security staff, Bill, a kindly and wise ex-policeman.

"Are they all raving loonies in here then?" said the rude man.
"Only the ones who fail the test," said Bill.
"What's the test?" said the man.
"Well, we show them a bath full of water, a bucket, a jug and an egg-cup, and we ask them what's the quickest way to empty the bath," said Bill.
"Oh I see, simple - the normal ones know it's the bucket, right?"
"No actually," said Bill, "The normal ones say pull out the plug. Should I check when there's a bed free for you?"