This is not to be understood as exactly true in the rigour of it, but only comparatively and hyperbolically spoken; for David desired their preservation and Absalom's too: but it must be considered that Joab was now in a high transport of passion, which might easily hurry him into indecent expressions; and that David's carriage gave too much colour to such a suggestion; and that such sharpness of speech was in a manner necessary to awaken the king out of his lethargy, and to preserve him from the impendent mischiefs.
Related Commentaries of 2 Samuel 19:6
2 Samuel 19:6
6 In that thou lovest thine enemies, and hatest thy friends. For thou hast declared this day, that thou regardest neither princes nor servants: for this day I perceive, that if Absalom had lived, and all we had died this day, then it had pleased thee well.