The anti-semitism goes right back into the early history of the genre:
The oldest conspiracy of them all was that The Devil had the King's ear and he was pushing him to do evil. This figure of The Devil is then, over the years, replaced by Jews, communists, Catholics, Freemasons, the list stretches on to include extra terrestrials and ultimately Icke's shapeshifters.
Quote from previous entry on this topic
It always raises its ugly head whenever you start to seriously delve into the topic and like a drop of poison in a cup it rightly puts a lot of people, including me, off. Adolf Hitler used conspiracy theories to gain power. His like today would fit the subculture like a hand to a glove. It's for this reason, partly, that ideas such as holocaust denial are tolerated in conspiracy theory circles. Holocaust denial or, "the hollowhoax", as it is known, is nothing more than an attempt to revise the legacy of the Nazis by people on the far right. It's put forward by people who are ultimately sympathetic to the Hitlerian cause. It's also frankly rather silly and, as a symptom of the nasty anti-semitism that refuses to leave the scene, doesn't have mainstream appeal.
This in my opinion partly accounts for the fact that, David Icke, and Texas talkshow host, Alex Jones, are easily the most popular conspiracy theorists around. They both wholly reject the anti-semitic aspects of the genre and so are more digestable by reasonable people. However they do still carry this second "we're all doomed, can nothing can save us" bit. It is in my opinion equally tiresome but less obviously absurd. Furthermore it is absent from their personal worldviews but apparent in their words to those who are, for want of a better word, "uninitiated".
I've slipped into this pit myself, probably most people reading this have*. A profound pessimism that 'the world is run by poweful people and they've got the game sewn up in their favour' speaks to most of us at some point or other. You don't have to be a conspiracy theorist to feel it of course and I think that's why the genre has such appeal. It confirms this intuition that you will never win the game of life.
The reason this feeling of helplessness is so integral to conspiracy theory is because of the fact that its roots are sunk so deeply into a bedrock of religious thinking. This is not so apparent when you give the likes of Icke and Jones a cursory glance but both of them are inspired by deep spiritual beliefs. Icke, although a little bashful on the topic these days, believes he is guided by a voice or 'spirit entity' and Jones is a committed Chrisitan. This aspect of their character is crucial to their worldview and it's the missing piece of the puzzle for a lot of their superficial 'fans'.
The cry of "we're all doomed; can nothing save us now?" has an answer in God. It speaks to the fact that this subculture is often used as a recruiting tool for cults (Jim Jones was a keen conspiracy theorist) and other religious faiths. It's the pretext to that old refrain "let us prey" but it deliberately leaves the Godless feeling helpless.
However, it's worth looking at the intuition behind the thought. This feeling that 'you cannot win the game of life'. Without wanting to push my own 'spiritual beliefs' I refer to the ideas of a Discordian High Priest and Zen Buddhist, Alan Watts. He spoke of the fact that this truth is more about emphasis than anything else. Yes, you will never "win" the game of life. You can express this as a sigh if you like, "oh, I can't win". Or you can express this as in excitement as if realising a revelation "ah, I can't win!". As in, "I can't lose!". There's no such thing as a winner or a loser. The universe and life do not judge you. The game of life is fun because you can't win. No one can. Those at the top of the pyramid are no better placed to win than you. The point of the game is to have fun and enjoy it, not to win and lose. You play the game of life in the same way you might dance from one end of a room to another. A dance is not about getting from A to B, it's about enjoying the motion, movement and music.
Further Alan Watts: http://www.youtube.com/watch?v=29atSZKbmS4