Ignorantly dishonest

What would be a good single-word for:

Someone who tells a lie but he doesn't know he's telling a lie.

Someone who, because of his own ignorance, spreads incorrect lies as universal truth.

Solution 1:

Single word: mistaken

mistaken adjective
wrong in one’s opinion or judgement:
   she wondered whether she’d been mistaken about his intentions
   • based on or resulting from a misunderstanding or faulty judgement:
      don’t buy a hard bed in the mistaken belief that it is good for you

[ODO]

I don't believe one can be ignorantly dishonest. Such a person as you describe honestly believes what he's saying, but is ignorant of the truth. A less charitable expression than mistaken is speaking from a position of ignorance.

Solution 2:

How about delusional or deceived?

delusional - adj. form of delusion:
1. a mistaken or misleading opinion, idea, belief, etc ⇒ he has delusions of grandeur
2. a belief held in the face of evidence to the contrary, that is resistant to all reason

self-deception or self-deceit:
the act or an instance of deceiving oneself

_{Definitions from Collins Dictionary}

Solution 3:

The word misfeasance is legal terminology. It refers to someone performing incorrectly even though it is legal. (This is broader than lying when you don't know it's a lie.)

(Misfeasance is contrasted with malfeasance, which is known wrongdoing by a public official.)

If the speaker spoke the truth literally, but intended for the listener to misconstrue the statement, then he spoke a prevarication. (If someone asks about your education, and you say, "I went to Harvard," then you are prevaricating if you merely visited the campus and intended the hearer to think that you were educated there.)

Other possibilities:

telling an innocent lie

telling an unwitting lie

being a tale-bearer

I am reading Living Economics: Yeseterday, Today, and Tomorrow. Peter J. Boettke says

The Keynes of The General Theory was never right when it came to an an economy operates, let alone how to fix it when it teeters during crises.

While Boettke does not use a single word to describe this phenomenon, he might name a Keynesian as someone who "spreads incorrect lies as universal truth."

Solution 4:

A "gossip" is someone who spreads information that may or may not be true, making the gossiper an unwitting liar if the information they're spreading is false.

Solution 5:

Unverified/incorrect information could be called misinformation. (The Free Dictionary distinguishes it from disinformation, the intentional spread of false information.) One who spreads misinformation is a misinformer.