From Answers.com http://www.answers.com/topic/black-legend

"Exaggerated and lurid accounts of the Roman Catholic Inquisition in Spain were, in the 16th century and still today, principal sources for the anti-Spanish Black Legend. The Inquisition had existed in many European countries before it came to Spain. It had existed in the Kingdom Of Aragon for some two centuries but not in Castile until the year 1480 when the Catholic Monarchs, Isabel I of Castile and Ferdinand II of Aragon, approved its establishment throughout Spain with the converso and Dominican friar, Tomás De Torquemada, as its first Inquisitor General, primarily to investigate and punish Judaizing conversos, Jews who had converted to Roman Catholicism but had continued practising their religion in secret."

"Some of the strongest and earliest support for the Legend came from two Protestants: the Englishman John Foxe, author of the Book Of Martyrs (1554), and the Spaniard Reginaldo González de Montes, author of the Exposición de algunas mañas de la Santa Inquisición Española (Exposition of some vices of the Spanish Inquisition, 1567). Another early source from which the Black Legend drew support was Girolamo Benzoni's Historia nuovo (New History), first published in Venice in 1565."

Others have argued that much of the Spanish Inquisition was the result of Religious Pogram

Regarding how much of the Black Legend was actually a more a result of politics than religion, Edward O'Brien in his article A New Look At The Spanish Inquisition notes that "In the 16th century, Catholic Spain was the great continental power. Her Protestant enemies were jealous of Spain and many resorted to lies to help bring down Spanish power and control. Spaniards were described by Northern Europeans as dark, cruel, greedy, treacherous, ignorant, and narrow. The Inquisition was fiercely attacked with gross exaggeration. Thus, a combination of political rivalry, contempt for the Catholic faith, and anti-Spanish racism created a distorted image of the Inquisition."

In that vein, Italian Catholic writer Vittorio Messori, claims in Crusades Truth And Black Legend that the Enlightenment cast a Black Legend shadow on the Crusades, and used it as a weapon in its psychological war against the Roman Catholic Church. In an article in "Corriere della Sera," Italy's most important newspaper, Messori wrote, "In order to complete the work of the Reformation, it was 18th century Europe that began the chain of 'Roman infamies' that have become dogma."

Another area to look at are comparitives between Protestand And Catholic Forms Of Inquisition, and which would include Witch Hunts, etc