Not withstanding the obvious copyright infringement and legal issues. It is only polite to cite your sources, if for no other reason than to let the people you are debating know what they are up against. If you find that someone else can better express your thoughts on a subject than you can then give them credit.
It is almost impossible to stop and check every single paragraph in some of the tomes that are written in these threads but some of this is obvious folks. Not everyone on here is a Bill O'Reily or James Carville or Rush Limbaugh. Please make the proper citing or links to use outside material.