The F-word in question? "Fascism".
And who is saying it? Conservatives. Specifically, The American Conservative magazine.
Here is the money paragraph:
And yet the very fact that the f-word can be seriously raised in an American context is evidence enough that we have moved into a new period. The invasion of Iraq has put the possibility of the end to American democracy on the table and has empowered groups on the Right that would acquiesce to and in some cases welcome the suppression of core American freedoms. That would be the titanic irony of course, the mother of them all—that a war initiated under the pretense of spreading democracy would lead to its destruction in one of its very birthplaces. But as historians know, history is full of ironies.
Frankly, I think this goes too far. Bad as the Bush Administration has been, I don’t think they have led us to the end of American democracy. No, they have merely walked us a few steps in that direction. Anyway, for an interesting perspective — one you may not have entertained before — read the whole thing.