"And they went and came <to Moses and to Aaron and to all the congregation of the children of Israel>…" (Numbers 13:26). "And they recounted to him and said: We came <to the land to which you sent us, and it does indeed flow with milk and honey, and this is its fruit>…" (ibid., ibid. 27); "However, <the people that dwell in the land are> strong…" (ibid., ibid. 28). Such is the way of those who recount slander: they open with what is good and conclude with what is evil.
How the Spies Opened With Praise and Closed With Slander
Midrash Tanchuma Buber, Sh'lach 17:1
וילכו ויבואו וגו' (במדבר יג כו). ויספרו לו ויאמרו באנו וגו' (שם שם כז), אפס כי עז וגו' (שם שם כח), כך דרכן של מספרי לשון הרע, פותחין בטובה ומשלימין ברעה.