The passage clearly states Brod's controversial nature right in the first sentence: "perhaps the most controversial figure is Max Brod". It then proceeds to explain why he is controversial, presenting a paradoxical situation:
- On one hand, he is indispensable: "Although it is thanks to Brod that we possess any of Kafka's writing-Kafka only allowed his writing to be published at Brod's insistence and had asked Brod to burn all his writing upon his death, which Brod did not do..." This shows he saved Kafka's work.
- On the other hand, he is criticized: "...Brod is considered by many Kafka specialists and enthusiasts to have possessed a meager understanding of his friend's writing and importance." The passage further elaborates on this criticism, noting the contrast between Brod's "blunt and crude" compositions and Kafka's "abstruse elegance," and their contrasting personalities. This leads to the concern that Brod "in some ways tainted the 'pure' Kafka in the editorial process."

So, the controversy stems from the fact that while he saved Kafka's works, he is simultaneously believed to have misunderstood them and potentially altered them negatively.

Now let's evaluate the options:
- (A) Although Brod was Kafka's closest friend, many wonder if Kafka objected to Brod's editorial alterations of his writing. The passage mentions concerns about Brod tainting Kafka's work in the editorial process, but it doesn't state that Kafka himself objected to Brod's alterations during his lifetime. Kafka's request was to burn all his writing. The objection comes from Kafka specialists and enthusiasts after his death, regarding Brod's understanding and potential influence.

- (B) Because of the divergence of their upbringings, Brod and Kafka had difficulty seeing eye to eye with one another. The passage mentions their contrasting personalities ("Brod being gregarious and a notorious womanizer, whereas Kafka was withdrawn and shy") but doesn't specifically attribute their disagreement or Brod's poor understanding to divergent upbringings. It attributes Brod's poor understanding to his writing style ("blunt and crude") and his personality in contrast to Kafka's.
- (C) Although he is the only source of Kafka's writings, Brod is thought to have poorly understood Kafka's writing. This option perfectly captures the central paradox and the reason for Brod's controversial status as presented in the passage. He's the reason we have the writings ("only source"), yet he's criticized for not understanding them well ("poorly understood").
- (D) Brod's lascivious behavior repulsed Kafka, who wished for someone more refined to edit his work. The passage mentions Brod was a "notorious womanizer" and Kafka was "withdrawn and shy," implying a personality contrast, but it never states that Kafka was repulsed by Brod's behavior or that Kafka wished for someone else to edit his work for that reason. Kafka's wish was to burn his work.
- (E) Upon Kafka's death, Brod burned all of Kafka's remaining writings, suggesting that he did not properly recognize his friend's incredible talent. This is directly contradicted by the passage, which states Brod "did not do" (burn all his writing) what Kafka asked. In fact, the passage credits Brod for saving the writings.

Therefore, option (C) is the most accurate and comprehensive explanation of why Max Brod is considered a controversial figure according to the passage.