(colloquial, rhetorical question) A reply to an unimportant or irrelevant statement, indicating indifference on the part of the speaker.
(colloquial, rhetorical question) A reply that dismisses the importance of another speaker's immediately preceding statement.
Source: en.wiktionary.orgThe opposite of the religious fanatic is not the fanatical atheist but the gentle cynic who cares not whether there is a god or not. Eric Hoffer
The charlatan takes very different shapes according to circumstances; but at bottom he is a man who cares nothing about knowledge for its own sake, and only strives to gain the semblance of it that he may use it for his own personal ends, which are always selfish and material. Arthur Schopenhauer
A patriot is someone who cares what happens in their country. Billy Bragg
Who cares about every little feather should not make the bed. Swiss Proverb
If it's not here and now, who cares about what and when? African Proverb
Who cares if a crow is male or female? Japanese Proverb