Shaykh Uthmān al-Khamīs expands on Shaykh Sālih al-Fawzān’s answer
The asl is salāmah, and Husn al-Dhan. Until proven otherwise.
Questioner: Is it permissible to say the foundation with every Muslim is Tawheed and Sunnah, until there is evidence proving otherwise?
Shaykh Saleh al-Fawzaan hafidhahullah: Yes, have good thoughts of the Muslim, unless otherwise is made clear