Max Lerner, an educator, journalist and student of American civilization who was for many years a syndicated columnist for The New York Post, died yesterday... He was 89 ... Mr. Lerner was one of the more conspicuous of the post-World War II nonfiction writers, a humanist whose unabashed liberal conscience led him to the political barricades for more than three decades. Many of his concerns now seem prescient. In 1959, for example, in a speech at Douglass College in New Brunswick, N.J., Mr. Lerner called for the formation of an antiwar elite, making it clear that he was worried about what he saw as growing mediocrity among American students.