What does 2 Samuel 16:21 mean?

Ahithophel said, 'Sleep with your father’s concubines, the ones he left to take care of the palace. Then all Israel will hear that you’ve made yourself hateful to your father, and everyone with you will be encouraged.' 2 Samuel 16:21 - Modern Text Bible

(Ahithophel advises Absalom to publicly claim David’s concubines, making a bold statement that he’s taken over, which would rally his supporters.)