How can one obtain sources that clarify the differences between Sunni and Shia beliefs, without directly accusing the Shia of error, to help a Shia man search for the right path before marriage?

The differences between Sunnis and Rafidah are fundamental. The Rafidah claim the distortion of the Quran, revile the Companions, and exaggerate regarding their imams, worshipping them, and preferring them over prophets and angels. They perform pilgrimage to shrines and graves, where they practice polytheism. They believe in hypocrisy (taqiyya), bada', raj'a, the absolute infallibility of the imams, and the doctrine of at-tinah (the clay). It is advised not to marry them.