It is narrated from Imam Hadi (AS) who said:

Whenever the observance of the justice is more than oppression and cruelty in a society, then it is Haram to suspect and distrust people; unless it becomes clear by certainty (that someone is not a good person). But if at any time, oppression and cruelty dominate justice, and then having favourable opinion for everyone is not appropriate; except if there is a certainty that an individual is a good person [1].

[1] Mostadrakul Wasa’el, Vol. 9, Page 146.

Source: en.shafaqna.com