Hi,

The logic (or rules) behind a normal colon usage seems to be that the part that follows the main clause give details or explain some parts of it, like going from general to specific. Why are they correct if they are? Generally speaking, they are giving an explanation, or you might say going from general to specific. 

Follow orders from those high up: whether to the king, as the supreme authority, or to ...

My wife says every man she's been familair with would smell his socks at night before he went to bed: just a whiff--each sock, no only one. [Edward Hoagland "The Problem of the Golden Rule"]

Millions of peasants are robbed of their fams and sent trudging along the roads with no more than they can carry: this is called transfer of population or rectification of frontiers.  -- Can we use a dash here? I think a dash is better  

My advice is never to use dashes. They are almost always the lazy person's method of expressing meaning.

My advice about colons is that you should only use them if you have superior English writing skills. Even with good writing skills, some people never use them. If you really want to use colons, don't use a lot of them or you will start to irritate the reader because the reader often has to make an effort to understand why you are using a colon, just as you have had to make an effort with your example here.

Best wishes, Clive