Is seeing a friend's wife talking on the phone with a mutual friend considered a reprehensible act that must be changed?

Muslims must be assumed to be in a state of well-being until proven otherwise. Therefore, it is impermissible to harbor ill-will towards a Muslim merely because one sees him speaking with a woman, without ascertaining the true nature of the conversation. If it is established that the conversation is religiously forbidden, then one must denounce the perpetrator, based on the Prophet's (peace be upon him) saying: "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart." The phrase "Indeed, I fear Allah" serves as a reminder of the evil and a deterrence from it. The righteous predecessors used to denounce with similar expressions, such as "Slowly, slowly, may Allah bless you," and "Indeed, Allah sees you both." If the perpetrator of the evil does not desist and repeats the act, then he may be threatened with informing the husband.