Anecdotes that Infessura relates may be colored by his own partisan nature, but his diary faithfully records news that was making the rounds in the city, whether true or not; "he inserted every fragment of the most preposterous and malevolent gossip current in Roman society, and is therefore not considered a reliable chronicler" (New Catholic Dictionary).
Infessura's diary, partly in Latin and partly in ancient Romanesco, the Diarium urbis Romae (Diario della Città di Roma) is of special firsthand value for the pontificates of Paul II (1464-1471), Sixtus IV (1471-1484), Innocent VIII (1484-1492), and the beginning of Alexander VI's pontificate.
According to the Catholic Encyclopedia, "Under Sixtus IV, his office was affected by the financial measures of that pope, who frequently withheld the income of the Roman University, applied it to other uses, and reduced the salaries of the professors".
That may not provide adequate motivation for Infessura's deep opposition to Sixtus' policies, and for anecdotes that would be certainly scurrilous if they are untrue.
As the Pope sank into a coma, "the harrowing story was told that, at the suggestion of a Jewish physician, the blood of three boys was infused into the dying pontiff’s mouth (the concept of circulation and methods for intravenous access did not exist at that time).