What is the meaning of Al-Shafi’i’s saying: "Let your suspicion be only ill, for suspicion is among the most powerful shrewdness; nothing has thrown man into distress except good suspicion and pleasant speech"?

The two mentioned verses are attributed to Imam Al-Shafi'i, but Dr. Ayed Al-Qarni denied the authenticity of this attribution. Their meaning encourages having a bad opinion of people or considering it prudence, despite the fact that having a good opinion is required of a Muslim, as Allah Almighty says: "O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin." Even if the attribution were true, Imam Al-Shafi'i is not infallible, and only that which is correct is taken from his sayings.