English expression for "ascribing negative intentions to someone"

The word "impugn" functions that way:

"Stop impugning my words."

To a certain extent, "mischaracterize" and "misjudge" have a similar nuance.

A person who derives an interpretation incorrectly, or from ambiguous data without seeking clarification, is jumping to conclusions.

A person who does it intentionally is maligning or impugning (thanks, @TheRaven).

I can suggest the word insinuate in terms of "implying a negative or unspoken fact"

b : to impart or suggest in an artful or indirect way : imply

I resent what you're insinuating

A phrase for you is "twisting my words"

twist someone's words (around)

to restate someone's words inaccurately; to misrepresent what someone has said.

Stop twisting my words around! Listen to what I am telling you! You are twisting my words again. That is not what I said!

For words, "putting words in my/your mouth".. otherwise, I think distrustful fits. But also faultfinding or even cynical?

The word pessimist may work too, but generally.