I didn't know it. [1] says it means "even a person of low status or importance has rights". The janitor in the story has rights, like he can certainly try to call the CEO to pitch an idea. Is that what you meant to point out? I feel like I'm missing out on the profoundness.
[1] https://idioms.thefreedictionary.com/a+cat+may+look+at+a+kin...