either from inexperience, laziness, or the mistaken belief that it seems you share that this form of hacking doesn't happen often in Steem.

So what youre basically doing is saying people are irresponsible with their funds thus need to be babied.
Thats a poor argument. Hacking and phishing i wouldnt put into the same category. Pure hacking coming from the failures in the STEEM code i find very unlikely and a risk that we should have accounted for when investing while phishing is again a product of people not being responsible with their funds.

Stopping change because a small minority of irresponsible individuals cant/wont take care of their funds properly is wrong on so many levels.

in Steem, users often use their keys in many web-based dapps.

Thats not really true. Keychain, SteemConnect.
If they do, thats another argument from the position of:
"Well, people are irresponsible and they dont know what theyre doing."

Lets educate them. Its very simple...

Dont give strange people you dont know your keys.

Then theres millions using exchanges where you basically give your funds away to a third party.

I'm only arguing that it is feasible to speculate on Steem without powering up SP (and hence keeping liquidity of purchased Steem). Now while it doesn't sound like you want speculators, some do

Hmm. Not powering up is extremely costly in lost ROI and inflation (2% yearly + 15% average from curation + 8%inflation) which is why, i assume, we lost many of our speculators. Shorter powerdown times would remedy that since STEEM mobility would be much greater

Im not saying speculators are bad, im saying that "our" speculators are bad since everyone that really believes in Steem is most likely powered up and not participating in trading to high degree.
I think thats safe to assume.
Reducing powerdown times would potentially increase the likelihood of (lets call them) hardcore hodlers to partake in the marketplace which would in turn increase liquidity, "health" of the token market and would create upward pressure on the price since those that believe in Steem are more likely to buy back in.

I think you're making a poor argument by labeling this "fear-mongering" as some kind of perjorative.

But it is fear-mongering.
Its basically the definition of it. Heres a quote from wikipedia.
"Fearmongering or scaremongering is the spreading of frightening and exaggerated rumors of an impending danger or the habit or tactic of purposely and needlessly arousing public fear about an issue."

The phishing that happens is a product of personal irresponsibility just like holding your funds in exchanges is. People still do it.
The point is not basing decisions on people being irresponsible.
Lets teach them otherwise.

On a side note... Just as a funny observation.... Crypto folks are the last people i ever thought would be so concerned with losing money.
-96% since ATH... lol