"Why the assumption that Past = Right/Conservative and Future = Left/Progressive?"
No, that's not really what I am saying ... and you are correct, that would be a very blunt oversimplification (or just plain wrong).
What I am saying is that in an unbroken thread of society (that is, absent disaster or revolution or other "resets") views and mores become viewed as more and more conservative by each successive generation that succeeds them.
As I wrote, "progressive people, and their opinions, turn into reactionary conservatives with nothing but the passage of time." I don't mean that those people become conservatives, I mean that successive generations view them as more and more conservative.
I don't think that implies that conservative views are backwards - unless you start with an assumption that "new is always better". I don't assume that.
I understood your original point. Implicitly, you are assuming that people develop their values and beliefs and lose plasticity over time, so they will not adapt to the societal changes happening around them.
I think the underlying thought experiment "would I want to be immortal" is plagued by these and other unspoken assumptions. We simply don't know what it would mean to have a lifespan decoupled from our evolutionary experience. Clearly, we have psychological and emotional development coupled to our physical development and our functional roles within human society.
What does it mean to freeze our physical health at our "prime" of 20s-30s? Would it also freeze our cognition and emotion? Or would an accumulation of experience still shift our minds into very different modes incongruent with what we assume of young adults? Think of idioms like "young at heart", "wise for her age", or "has an old soul". Will people freeze with one personality, or all trend towards some world-weary and sage disposition as they witness more and more of life and loss?
And what of pathologies and maladaption? When would people reproduce, if they are immortal? Where does evolutionary pressure provide feedback, if traits can erupt with arbitrarily inter-generational delay?
Can an economic and social system develop to handle immortal participants? The worst aspects of primacy could emerge, if actual individuals can take the place of dynasties and corporations as permanent centers of wealth and power. Conversely, would any potentially immortal individual want to take on great personal risk for the betterment of a larger group? How does this change with time? Would centuries of experience lead one to sacrifice for the young, or would the absence of decrepitude encourage selfish delusions of grandeur, thinking that an accumulation of vast experience should be preserved by spilling blood of relatively empty youth...?
"I understood your original point. Implicitly, you are assuming that people develop their values and beliefs and lose plasticity over time, so they will not adapt to the societal changes happening around them."
With respect, we're talking past one another.
I am not talking about the persons whose lives are extended.
I am talking about their new contemporaries - their "younger peers" who, in the past, would have never found themselves cohabitating with people who had lived 1xx or 2xx years ago.
It is those future young people who I think will have a very hard time accepting any views of any kind coming from any "great old ones" - no matter how plastic or malleable or open-minded those old people might be.
Their sin is simply being old and youth defines itself by breaking with the old. Right now there's a throttle on that struggle because people die. Without that throttle, the young will, I fear, kill the "vampires".
To me, you still seem to be implicitly assuming that the old person would be reflecting "old" perspectives. I don't necessarily disagree with this assumption, but I think you may be overlooking how much your argument depends on this. And, I am not sure that the dreamers of life extension share this assumption.
Playing devil's advocate: If one had the permanent physical and cognitive characteristics of someone in their 20s-30s, might they not continue to pass as a young person? Unless you look up their identity in some registry, you wouldn't necessarily be able to identify a cohort. Here is urban Southern California, I see plenty of "old" people in their 50s-60s who are trying to pass as young people all the time. What if they don't have to mask fading hair and eyes, sagging or blotchy skin, aching joints, gravely voices, or personality changes?
You describe a person from 200 years ago existing today, as if they step out of a time machine. But, if they have had 200 years to absorb pop culture, mannerisms, dialect, etc. then how would you know? They won't be repelled by garlic nor invisible in mirrors. They won't even be afraid of sunlight (no skin aging!) and their blood-sucking may not be distinguishable from any young go-getter's.
No, that's not really what I am saying ... and you are correct, that would be a very blunt oversimplification (or just plain wrong).
What I am saying is that in an unbroken thread of society (that is, absent disaster or revolution or other "resets") views and mores become viewed as more and more conservative by each successive generation that succeeds them.
As I wrote, "progressive people, and their opinions, turn into reactionary conservatives with nothing but the passage of time." I don't mean that those people become conservatives, I mean that successive generations view them as more and more conservative.
I don't think that implies that conservative views are backwards - unless you start with an assumption that "new is always better". I don't assume that.