Why didn't men like The Color Purple? Why did Alice Walker feel justified in writing it anyway?

The previous answer was very strong.  I might want to add that the notion of men not liking the work might be better framed as being disdainful of the novel, as much as being challenged with a new frame of reference.  What makes the work so much of a force to the traditionalist notions of narratives is that it asserts and advocates for the voices of women.  The female narrative structure helps to provide voice where there was silence and helps to create a new voice in the discourse.  This is a challenge to any particular structure, and the forceful and clear nature in which Walker's work resonates in the conversation of narrative and identity might be a reason why there was such an intense reaction to it on the part of men.  It might not have been dislike as much as being introduced to a new voice, which is always a process where there is reticence and hesitation.  Over time, if the narrative is emphasized and underscored with greater regularity, it becomes an established voice in the diaspora of thought.  This might be proven with the work, itself.  Walker's themes and characterizations of men would not be seen in the same light of "shock" and "dislike" now as they were when they were first introduced.