Great point.

I think that Moderatism - by my sloppy definition - would also qualify as one of these ideological movements, the difference being that its core premise is "Polite dinner conversation is the be-all-end-all to politics: don't get controversial!"

Idealogical movements tend to start off with One Great Idea, which happily explains about 70% of reality by its heuristic, and then covers up the other 30% with 'Just So' explanations. Regardless of their roots, they become creatures designed for mass appeal - rather than rationalistic theories to explain reality.

Ignoring the party-specific heuristics, and looking at the tenets themselves, I come across some ideas which I'm extremely certain of, and are often the most radical within the movement - crazy ideas which have trouble flowering without the supporting manure of the rest of the ideology.

For instance, on the fringe Right: -Gay sex is a major health hazard, given the infection rates of HIV (roughly 700 times as dangerous as straight sex) -There are almost certainly intellectual and behavioural differences between the races -Patriarchal forces are far less damaging than Feminist ideology

On the fringe Left -Institutional violence is a distinct reality, with many specific examples which can be pointed to -There is no line in the sand between legal drugs and illegal drugs; you cannot differentiate between the two; heroin should be legal -The primacy of individual liberty is the only sane way to organize a society

Every camp has a few things that it's right about - Marxists, Anarchists, Statists, et cetera - but the individual tenets are extremely uncomfortable to hold or argue without (for example) buying into all of the comfortable delusions that Sarah Palin exemplifies (if you're a Conservative). It's easy to shout "I am an anti-Statist! Racism is bad! Borders and immigration laws are wrong!" It's far more difficult to say "I'm an anti-Statist, and racism is a poor heuristic, but importing people with no skills, and no cultural history of Classical Liberalism is a danger to our society."

I guess what I'm saying is that while this approach necessarily dissolves radical ideologies it doesn't necessarily affect radical ideas.