Patur Avul Assur.
Bringing a Teshuvah regarding the Refuos written by Chazal is not really going to get you anywhere unlesss you are completley unaware of the wide ranging Machlokes about being reliant on what Chazal say regardin Refuos.
However to try and address your point’s more specifically.
You really do not have to try and find an obscure Teshuvos Geonim to try and bolster you’re point. There are more mainstream one’s (very few but they exist I have hinted at one of them in my posts. I don’t know if they come up in aGoogle search though.
You see the “man on the street” view and the one Slifkin would like the average person to think is that the Gedolim called him a kofer becuase he stated that Chazal did not know science.
That’s blatantly false, it’s a lot more nuanced then that and actualy requires a level of understandign that comes from learning Torah inside, it does’nt really come from Google.
Slifkin advocates a form of learning he calls Rational Judaisim.
In his books he dances around it without advocating his world view openly but if you understand what was being written it’s there as well.
Now this “philosphy” of his which he cals Rational Judaisim is based on nothing.
Absolutley Nothing.
He has no sources and not a leg to stand on.
Does he have backing for individual points?
I’ll give an example’s I’ve given before, and try to be more clear, perhaps you’ll stop ignoring them.
Rav Shamshon R. Hirsh zt”l wrote a letter about aggadita where he expresses the opinion that “it seemes to him that Chazal based there opinions of Science on the secular knowledge of their day”.
See? RSRH is a pretty mainstream view and was one of the Gedolim of his time.
So Slifkin would seemingly have a “source”.
The problem is that Slifkin takes this opinion and runs with it and attempts to interpet statements and opinions of Chazal on a “Rational Basis”, he build’s upon the opinion he identifies as that of RSRH to advocate an adoption of his understanding of Moreh Nevuchim’s approach to Aggadita.
Now the only problem is that one of the most detailed and forceful condemnation’s and refutation’s of Moreh Nevuchim ever written down and published to a wider audiance was that of RSRH zt”l in the last of the Nineteen Letter’s!
RSRH actually maintained that Moreh Nevuchim had done more damage to Klal Yisroel the Moses Mendelsohn!
And bear in mind the target audiance of The Nineteen Letter’s was the exact audiance that Slifkin claims to be introducing his philosophy for.
Rav Shamshon R. Hirsh’s written letter about Moreh Nevuchimm was so forceful and detailed that when The Nineteen Letter’s was published in Hebrew the Chazon Ish told the publisher’s to leave out that part for fear it would be misunderstood!
So using RSRH to justify introducing Moreh Nevuchim as mainstream is somewhat problematic.
So let’s leave RSRH aside and take the Rambam in of itself, Slifkin advocates his “Rational Judaisim” as a Maimomodean approach of examining the statments of Chazal on a “rational basis” with an understanding they may ch”v have been plain “Wrong”.
Agin though the Rambam himself writes quite clearly in several place (the most detailed of which I have translated above), that one who takes this approach is a “fool” and “cursed”.
So you see cutting and pasting qoutes won’t do.
The fact’s remain that Slifkin’s approach and understanding of Chazal does not have a leg to stand on and has been condemned at any time it has been advocated. Which is why his own Rebbi Rav Moshe Shapiro shlita called it kefira.