Answer :
The sentence in question reflects the author's challenge in balancing response to criticism and engaging in constructive work, demonstrating the necessity of prioritization due to limitations of time and effort.
The author's purpose for including the sentence "If I sought to answer all the criticism that crossed my desk, my secretaries would have little time for anything other than such correspondence in the course of the day, and I would have no time for constructive work" is to express the limitation of time and resources when faced with an overabundance of criticism. This notion is echoed in the provided references where authors discuss the necessity of prioritizing their efforts on worthy tasks over responding to every single piece of criticism or request. They highlight the importance of focusing on constructive work and significant projects rather than getting sidetracked by less constructive engagements.
The author is persuading readers that he doesn’t have his staff focus on correspondence because it is frivolous