I know that many, many other sites have gotten nastygrams for using too much of copyrighted articles. I have not seen another site that has a compiled list of rules by source as FR does, but I have also not seen another site that routinely uses outside articles as the basis for a thread as FR does.
If I tell you, you can't post that article on your discussion board because of the political slant you have, I am decidedly going against the First Amendment.
Nope. If I tell you you can't post *my* article -- for whatever reason -- I'm exercising my copyright. The first amendment prohibits the government from limiting speech and press except in severely limited circumstances. It does not prevent authors from controlling the use of their works.
Suppose The New York Times opted to prohibit FR, or bloggers, or anyone from posting any part of its articles. I don't believe that they ca prohibit a link, though that's an evolving area of the law. But they cannot stop you from saying "today's New York Times says 'foo,' to which I respond 'bar.'"
Exceptions, most notably fair use, exist to foster debate and criticism.
I promise you that I'm not being combative, but are you making this up as you go along? Exceptions are used to force the reader back to the source to give proper credit to the author.
Copyright law exists to allow authors to control the use of their work. Most copyright holders want to drive you to their own site, not just for credit, but so you see their ads and they get paid. Exceptions to the copyright laws, such as fair use, ensure that while you can't steal and sell someone else's work, you can discuss and criticize it.
For example, unless there's something I didn't notice in the FR user agreement, everything I post to FR is copyright (C) me. You certainly have every right to quote my post in responding to it, as you did above -- more so with a message board post, because that's the point of a message board, and if I didn't know that I'm an idiot. But you couldn't compile my posts in their entirety as a Web site or CD-ROM and sell them without my permission.