I have read in The Majlis that Sheikh Qardawi is a deviate.

Answer

One should not read/study the books of deviates and the people of baatil even if what they write is 100% in conformity with the Shariah. The reason for this is that the evil of their dhalaal and baatil permeates their pens, and this exercises a detrimental spiritual effect. Although it is not sinful to read such writings of the people of baatil, which are not in conflict with the Shariah, nevertheless, the spiritual effect is detrimental.