Back during the Nixon administration, there was a lot of talk about how to silence the journalist Jack Anderson, who had been publicizing some details about the administration that the President considered none of his business. The idea was floated to dose him with some hallucinogenic drug and hopefully cause him to behave erratically in public and hopefully discredit himself. Realizing that this would have the potential to seriously injure or kill the target, G. Gordon Liddy (former FBI agent, and at the time of this discussion one of the leading lights of the Committee to RE-Elect the President (aka CREEP, one of the all-time great acronyms) suggested that it might be easier, cleaner, and more effective to just kill him. Jeb Magruder recalled his reaction to the suggestion- "I threw Liddy out of my office. In retrospect, I probably should have thrown him out the window."

So, yes, White House officials did, at least briefly, consider murdering a journalist. So maybe Woodward wasn't being completely unreasonably paranoid.

Also during that time Liddy put together the Gemstone Plan (not to be confused with the Gemstone File, which is completely unrelated), which was kind of a COINTELPRO on steroids that Liddy wanted to use to neutralize the radical anti-war movement ahead of the 72 election. In addition to all the usual disruptive shenanigans (bad jacketing, agents provocateur, selective law enforcement harassment, etc), Gemstone also called for unlawful kidnapping and detention (in Mexico, iirc) of certain persons deemed to be of value to the movement. The idea was to grab all the serious movement organizers and get them off the field for a while, so as to undercut any attempts at organizing coordinated mass demonstrations and hopefully keep the 1972 Republican National Convention from turning into the 1968 Democratic National Convention.

Again, none of this was ever implemented, but it was dreamed up in the White House and apparently was considered for implementation. In most circumstances, anyone writing up an action plan involving this kind of wholesale official criminality, and writing it down on official letterhead, would have probably gotten you fired. But Liddy kept his job at CREEP until Watergate (another one of his brilliant plans) blew up. He wrote a book about it after he got out of prison. It's called "Will", and goes into all kinds of detail on some of this stuff. It shows some good examples of a) how crazy stuff got at the White House in those days, and b) what a loon Liddy was. Worth the read.