Hacker culture was not well established by the 70s, simply because so few people worked with computers in that decade. You can certainly trace its roots back to at least 1970, but it really did not become established then.
What most people identify as "hacker culture" today arose in tandem with (a) relatively affordable "personal" computers (b) modem-based communication.
The rise of these two things is more or less entirely cotemporal with the most productive phase of Dennett's career.
I consider this definitive evidence that the foundational period of hacker culture was before these books were published. I'm not sure what the point of trying to shift that period forward so as to include Dennett's works is. It's neither true nor necessary.
His first three books were published in 81, 84 and 86.
I agree with you that the foundational period slightly predates these, but I don't consider the foundational period to be the same as when "hacker culture was established".
I began to encounter it myself starting in about 1979 via CoEvolution Quarterly/Whole Earth Review, but it was still very, very much evolving and continued to do so in very noticeable ways as I started programming in 1984.
I tend to consider the general use of IP as probably one of the main signifiers of hacker culture being established, and that was far from common in the 75-85 period (though growing rapidly).
It wasn't actually my claim that Dennett had much influence on hacker culture. I was originally disputing the idea that Dennett became well known after 1992.
I'd argue hacker culture goes back much further than the 70s, e.g., with MIT hacks during the 1930s and 40s (see Feynman) and in Cambridge UK, as well as the early HAM radio enthusiasts in the 1900s...
There are certainly antecedents and ancestors for hacker culture long before the 1970s, but in the post I was replying to, the term used was "hacker culture was established", and I would argue that none of these early anticipatory elements represented the "establishment" of a new culture.
It’s the same culture made by the same people entering and leaving across that full period. Hacker culture is really a continuation of the same ad hock machinist culture dating back to the Industrial Revolution. It jumped to computers from the days of analog computers.
You can trace things flowing all over the place with say MIT’s Tech Model Railroad Club being often sited as an early example. But it’s really just refinements of the same basic culture, and computers is one of the few places it survived unlike say pinball.
I think about this a lot with reference to the mechanics institute in San Francisco. Who were these mechanics and why did they have a 4 story institute still home to a chess club and private library? Certainly not a direct crossover to a modern car mechanic, even a "hacker" type car mechanic wouldn't stereotypically also be thinking along the philosophy of hacker culture, although I am sure some do.
I do think its true that some of his work has resonated with many people who also resonate with "hacker culture".