The fallacy is that the finger pointers think that the tea party movement is a top down organization and it isn't. It is bottom up. And if it is a popular movement than the establishment has a tendency to want to co-opt it, claim it as their own.
This movement which leans right isn't much different than the net roots movement that wanted to take back the democrat branch of the democrat party. Remember Howard Dean?
The Tea Party is really an anti establishment movement. They are tired of business as usual, they are the third wave, somewhere in between the country club Republicans and the Evangelicals.
They may lean libertarian, they may lean Republican. They are who they are. What they all have in common is they don't want incumbents to get complacent.
Even Ron Paul, thought by many ( mostly his staff) as the father of the movement is facing primary chalenges from not one,not two but three persons associated with the Tea Party Movement.
http://www.dallasnews.com/sharedcontent/dws/news/washington/stories/DN-ronpaul_07tex.ART.State.Edition1.4bf50f3.html