Only if they do it twice.

The expressions "being fooled" and "being made a fool" have coexisted for a very long time.

at some point you have to trust something

I trust the floor of my bedroom to be there when I get up in the dark.

I trust my wife not to change the locks on the house when I'm out or not to murder me in my sleep

I trust my friends not to falsely accuse me of horrible crimes to the police

I trust the starbucks drive through is real and not a fake starbucks pretending to be starbucks

any one of these things could "fool" me at any time, doesn't mean I'm stupid.

however, what I never trust is that there is a secret to get ahead quickly. Whatever it is, it's always slow, expensive, with a lot of paperwork, requires practice and expertise, and will go wrong several times.

so if someone gave a hundred grand to someone who wasn't a known financial institution expecting a massive return on their investment with no paperwork, I would say they were foolish. If they were a close friend / relative, I'd commiserate and use kinder language to their face, something along the lines of they've got to take better care of themselves and their finances.- because I am a kind person. Some people believe in tough love. I believe such a concept is to be used very sparingly.

I'd say you're more likely to get a positive response if you use words like "deceived" or "conned" or "lied to" which place the fault on the deceiver.

"Fooled" isn't offensive per se; "chumped" is worse. But if I was wanting to convince someone that they had been maliciously given false information, I'd use language that doesn't raise hackles by implicitly blaming them for being deceived.

Edit: "Played for a fool" is more offensive IMO, because now you're pointing out that the victim has some exploitable flaw which allowed the deceiver to make a fool of them.

Edit again: Sorry for the double post. Something seems to be a little weird with my app.

I'd say you're more likely to get a positive response if you use words like "deceived" or "conned" or "lied to" which place the fault on the deceiver.

"Fooled" isn't offensive per se; "chumped" is worse. But if I was wanting to convince someone that they had been maliciously given false information, I'd use language that doesn't raise hackles by implicitly blaming them for being deceived.

I ate a salad, am I a vegetarian?

Fools are full of certainty. The wise are full of doubt.

Fool is a spectrum. E.g. take the saying "fool me once, shame on you; fool me twice, shame on me". It's possible to fool anyone. Sometimes it's because they are a fool, but sometimes it's not.

IF you learn, THEN only temporarily.

IF you don't/won't learn, THEN you ARE a fool.

That is exactly what it means, yes. Though people will probably feel less happy if you point it out explicitly

Not necessarily, it means someone else was smarter than you, or exploited a weakness of yours, which might be your kind heart or your greed, rather than a lack of intelligence. Note: kindhearted people won't mind being told this but greedy people will mind. "Scammed" or "exploited" put the onus on the perpetrator. If you already said "played for a fool " and they took offense, consider adding some of these types of synonyms if you want to mend their feelings.

As is all social interactions, context is key

Unfortunately the foremost expert on the subject is no longer with us