Put the meaning into your own words.

Calling the lost key unimportant sounded like a rationalization for carelessness.

A club officer continued to profess support for open participation while reserving every desirable workshop place for his friends. Members called the conduct hypocritical because he presented himself as a defender of the principle he was disregarding. His rationalization was that familiar faces always made sessions run better, a convenient explanation offered only after the reserved list became public.