The original take on Original Sin is that Adam exceeded his authority by telling Havvah not to TOUCH the fruit. IOW, his Humra was so easily debunked by the Nahash, and Adam's credibility was sunk - and so Havvah HAD to give into temptation! Or did she?
The Midrash adds [P. 1395] that Havvah slandered Adam in her mind "All that my teacher [I.E. Adam] instructed me is false"
NB: the brackets re in the original.
Thus we see, Hashem is giving Adam a Mitzvah. And Adam -acting as a "Rabbi" -violated "bal Tosif" by over-instructing Havvah and thereby enabling the Nahash to override the original Mitzvah, too.
But - what's the slander? After all Havvah seems correct! She was after all misguided by her Rabbi!
This "slander" is a secondary aspect and highly instructive to any Talmid who finds a flaw in the instructions of his Rebbe.
What happens when a Rebbe has apparently said something flawed, or even C"V something definitely flawed. What SHOULD be his/our reaction?
Let me re quote with emphasis "ALL that my teacher instructed me is false"
Well this itself is jumping to a false conclusion! Making an error might impeach one's credibility! Furthermore, even while Adam was not infallible, it does NOT mean ALL he said was ipso facto FALSE!
And so how Should Havvah and/or our hypothetical Talmid should have reacted to a perceived flaw in instruction?
1. "While there was a flaw in what my Rebbe said NOT All that my teacher instructed me is false" A Rationalist Approach
2. "Despite a possible flaw in what my rebbe said, SOMETHING, [I. E.some core principle] MUST be true even if he failed on some detail". The approach of a "Believer"
Had Havvah reacted so, and said "wait a minute, Nahash! Just because I CAN touch this fruit - it doesn't mean I should go ahead and eat it!". Had she exercised some caution here...
At any rate, this is not about berating Havvah, it's about teaching our hypothetical Talmid not to over-react and to throw out the baby with the bathwater.
Yes Adam erred on the side of caution, but this does not license one to throw caution to the wind
Many years ago, when I took my driver's test, my instructor told me
"Rich, the speed limit on the course is 25 MPH. But go about 20 anyway". I proceeded to go 15! And thus the inspector was impatiently at his wit's end! But even though he lectured me about being able to make quicker reactions, he DID pass me. My caution, though annoying, was not fatal!
Now imagine had I said to myself "my instructor said 20, but the sign really says 25 - so I'll do better and go 30!" I might still be trying to pass to this day! ;-)
As you see, "fools rush in..." Adam might be faulted for over-compensating, but some level of trust - of emunat hachamim - is a must for Torah Observance