为什厶用“black-sheep”来比喻“害群之马”？

意旨: 在一群纯白的绵羊当中,偶然会出生一头长黑毛的羊.

这只黑羊属于少数族类,而且黑色的羊毛也不及白色的珍贵.

所以黑羊多被视为无用之辈或不良份子.

黑羊其实挺古怪的,讨厌群众,宁愿寂寞.

不喜欢被注视,其实又渴望别人的关心.

无原因的发脾气.

可怜自己的身世却又孤芳自赏.


----------------------
有一次，黄帝要到具茨山去拜见贤人大隗（wei）。方明、昌寓在座一左一右护卫，张若、他朋在前边开路，昆阍（hun）、滑稽在车后随从。他们来到襄诚原野时，迷失了方向，七位　贤都迷路，找不到一个人指路。
这时，他们正巧遇到一个放马的孩子，便问他∶“你知道具茨山在哪吗？”
孩子说∶“当然知道了。”
“那厶你知道大隗住在那里吗？”
那孩子说∶“知道”
黄帝说∶“这孩子真叫人吃　，他不但知道具茨山，还知道大隗住在那里。那厶我问你，你是否知道如何治理天下呢？”
孩子说∶“治理天下，就象你们在野外邀游一样，只管前行，不要无事生非，把政事搞得太复杂。我前几年在尘世间游历，常患头昏眼花的毛病。有一位长者教道我说∶“你要乘着阳光之年，在襄城的原野上邀游，忘掉尘世间的一切。现在我的毛病已经好了，我又要开始在茫茫世尘之外畅游。治理天下也应当像这样，我想用不着我来说什厶。”
黄帝说∶“你说的太含糊了，究竟该怎样治理天下呢？”
“治理天下，和我放马又有何不同呢？只要把危害马群的马驱逐出去就行了。”
黄帝大受启发，称牧童为天师，再三拜谢，方才　开。
启示∶
对有损国家、集体、人民利益的团体或个人，要及早发现、及早处理。（或∶要虚心向他人请教；事物是相互联系的等等。）

On one occasion, the Yellow Emperor with Heights Mountain the worship Jianxian People's Congress Kui (wei). Fang Ming, Chang apartment here either side of the guard, Zhang if his friends in front of the open, Kunming Steel (hun,), the funny car followers. They came to the Xiang Cheng wilderness, lost its way, the seven sages are lost, can not find a person guiding.
At this time, they happened to encounter a child put the horse and asked him: "You know with Heights Hill in what?"
The child said: "Of course."
"Then you know that the large Kui lived?"
The child said: "I know"
Yellow Emperor said: "This child is really astounding, he not only with the Heights Hill also know that the large Kui lived. So I ask you, do you know how to control the world?"
The child said: "governance of the world, just like you in the field excursion, like just before the trip, not much ado about nothing, to the conduct of public affairs, too complicated a few years ago I traveled in the earthly, often suffering from dizziness, problems have a long Religion to me: "Do you want to brave the sun a year, on in Xiangcheng the wilderness excursion, forget about everything earthly. My problems, I have to swim in the vast World dust outside. Control the world should be like this, I think do not need me. "
Yellow Emperor said: "What you say is too vague, how to control the world what it?"
"Control the world, and I put your horse different? Harm the herd of horses expelled on the line."
Yellow Emperor inspired, said the shepherd for the Fearless, repeatedly thanked him and just leave.
Revelation:
Detrimental to the state, the collective interests of the people, groups or individuals, early detection, early treatment. (Or: the humility to ask others; things are interlinked and so on.)