Ah yes, the danger of thinking you can think for yourself.
The danger is that it avoids regression to the mean. For that reason, yes it is the most dangerous dogma, but it also has a lot of potential. I'd trust someone like this more than I'd trust your average "agreeable" neurotypical who can at any moment be convinced by a charismatic enough charlattan cult leader to do just about anything if the neurotypical is down on their luck. Yes, some people like this have dangerous beliefs and a dangerous tendency to act on them but at least you can usually see them coming.
Also, what if they are free from dogma? What if they just think better than you or I? Depending on how free they are from dogma the danger may just be that they are excellent rationalisers. If someone who I think is mostly someone who thinks for themselves: they view every claim critically and insist on rederiving every conclusion before they believe it, if they tell me theythey are totally free from dogma and the masses are brainwashed idiots they're probably wrong about the "entirely". But, more or less, they are right. The only danger here is you can't talk them out of things, if they think you are one of the brainwashed masses and they might be angry about most people being brainwashed.
If they are a typically dogmatic thinker then they are really good at believing things which aren't true which presents a whole different kind of danger. Also they probably think of people who disagree with them as evil mutants and themselves as noble saints.
It's not dangerous for someone who is better at thinking undogmatically than people in general to found their philosophy on this difference, or even the overestimation of it that you propose.
Can you link the scary moment of dogma from the blog of a certain locally famous software engineer? Is it paul graham?
In a comment below you say "intolerance for "blindness" or "delusion", the insistence that there's one calculable right way to run things is culturally destructive." You sound like you are talking about something completely different. I suspect thinking they are free from dogma is simply something people who think there's one calculable right way to run things happen to tend to do and you are throwing out the baby (okay, maybe a crocodile) with the bathwater. Thinking that demonstrates blindness to the facts. Thinking that one's preferences are objective pronouncements on how the world should be in some fuzzy non value dependent way demonstrates that you mistake your feelings for facts. Believing you don't do this does intensify the danger such people pose massively but it isn't the source of the danger. And for people who don't do this, or don't do it very much, or who are just not abnormally vindictive or aggressive or callous enough to come up with a right way to run things that hurts people, or accept that their right way to run things will not be implemented are not a danger.
The certain software engineer is Mencius Moldbug, of course.
Related to: Reason as memetic immune disorder, Commentary on compartmentalization
On the old old gnxp site site Razib Khan wrote an interesting piece on a failure mode of nerds. This is I think something very important to keep in mind because for better or worse LessWrong is nerdspace. It deals with how the systematizing tendencies coupled with a lack of common sense can lead to troublesome failure modes and identifies some religious fundamentalism as symptomatic of such minds. At the end of both the original article as well as in the text I quote here is a quick list summary of the contents, if you aren't sure about the VOI consider reading that point by point summary first to help you judge it. The introduction provides interesting information very useful in context but isn't absolutely necessary.
Link to original article.
Introduction
Nerd Failure Mode
This section is the part most relevant to LessWrong:
In sum:
I bolded the note on mass literacy and participation because of the interesting historical conclusion that in the United Stated mass participation in democracy inevitably made the influence of religion on policy greater. It goes against a deep assumption shared by most educated people that "democratic elections" necessarily produce "liberal" or "secular" results. It was particularly evident among pundits and particularly easy to see as foolish with the recent upheavals in the Middle East.
This last rather minor seeming note is perhaps the most relevant part of the article for aspiring rationalist. Not only is it particularly salient for those us inclined to questioning the usefulness of the category "religion" in certain context, but because nearly all of us are not religious. Our bad axioms seem unlikely to originate directly from something like a religious texts, though obviously it is plausible many of our axioms ultimately originate from such sources.Not many of us are Communists either, but we are attracted to highly consistent ideologies. We seem likely to be particularly vulnerable to bad axioms in a way most minds aren't.
So if after some thought and examination you notice that a widely respected and universally endorsed axiom in your society has clear and hard to deny implications that are in practice ignored or even denounced by most people, you should be more willing to dump such axioms than is comfortable.