This a type of ad hominem attack that is very common on the left. When they say "why do you care" it means "you're just on the bad side". Your immediate answer should be to attack thier character for not caring. They are not arguing from logic so logic won't matter. But if you call them evil for thier position it destroys the foundation of thier ego centric ideology. Why don't you care that her lies destroy the credibility of all women? Why don't you care that by supporting a narcissistic liar you are associating all women with her? Why don't you care that defending her lies makes all of feminism complicit in her crimes? Etc. This should be applied to all ad hominem attacks presented as "Why do you care" questions.