"Don't say" refers to the meaning that is difficult to describe and express in words. It often implies some disgusting or unpleasant things or feelings, and sometimes it also indicates very bad behavior or character.
And "inedible" means inedible and inedible, and it also implies some negative and unacceptable quality or thing.
The whole sentence means that some people or things may pursue worthless, immoral or even evil things, but these pursuits are difficult to describe or describe in words.