Complex sentence: Parsons was disturbed by the rise of McCarthyism in the early 1950s, but in 1953 he wrote a letter to Oppenheimer expressing his hope that "the anti-intellectualism of recent months may have passed its peak".
Split into simpler sentences: Parsons was disturbed by the rise of McCarthyism in the early 1950s. In 1953 he wrote a letter to Oppenheimer expressing his hope that "the anti-intellectualism of recent months may have passed its peak".