In contrast to the absolute understandings of the ardent followers of Ibn Taymiyyah such as the modern "Salafists", from a more nuanced study of the Sufis we find that one of the greatest scholars of Islam Imam Ghazali was a Sufi and contributed significantly to the development of a systematic view of Sufism and to its integration and acceptance in mainstream Islam. Al-Ghazali belonged to the Shafi'i school of Islamic jurisprudence.
He was considered as the most important refuter of Mutazilites, the group whose interpretations were increasing the influence of Greek theology on Islam. He is even called by the title of Hujjat-al-Islam (the proof of Islam). However, Ibn Taymiyyah greatly criticized Ghazali for his interpretations. Interestingly, one of the most influential, probably the most influential before the 20th century Muslim scholar from the Indian sub-continent Shah Waliullah came to the conclusion that both Imam Ghazali and Ibn Taymiyyah were arguing the same thing with the difference being only of the angle.
The above is in reference to the Sufi and political interpretations of Islam and not on whether some sub-groups who claim to be following Sufi Islam also happen to be involved in deviant acts or not.
