There is a saying 下衆の勘繰り(Gesu no kanguri) in Japanese.
"Gesu" means a person who is mean, lowly, or base in his/her heart. "Kanguri" means interpreting falsely someone's intention as bad.
A translation of this saying can be: A mean person often interprets an innocent person's intention as bad."
Is there a similar saying in English? If not, what would you say to such a person?
"Suspicion always haunts the guilty mind" (Shakespeare, Henry VI, Part III, Act 5 Scene 6)
The original sense of the quote in the play is not exactly equal to the sense of the Japanese proverb, but when abridged, it might fit. Language is flexible.
In the original text, the full sentence is used to indicate that "a guilty person is always afraid of retribution":
Henry VI.
So flies the reckless shepherd from the wolf;
So first the harmless sheep doth yield his fleece
And next his throat unto the butcher's knife.
What scene of death hath Roscius now to act?Richard III (Duke of Gloucester).
Suspicion always haunts the guilty mind;
The thief doth fear each bush an officer.
The technical term psychological projection sounds similar. You might say, "You are just projecting your own intentions on him."
