Wasn't the altar a place of safety?

Adonijah had fled there in chapter 1: he "hung onto the horns of the altar" (1:50), and Solomon let him go home on a condition (1:52-53). Joab does the same: "Joab fled to the LORD’s Tent, and held onto the horns of the altar" (2:28). Held onto is chazaq, the verb of "be strong" (2:2), and in Hebrew the two phrases are the same words. When Benaiah tells him the king says to come out, Joab answers, "No; but I will die here" (2:30), and Solomon says, "Do as he has said" (2:31). One law in Exodus speaks of a killer at the altar: "If a man schemes and comes presumptuously on his neighbor to kill him, you shall take him from my altar, that he may die" (Exodus 21:14). Just before, for one who kills without meaning to, the LORD says, "I will appoint you a place where he shall flee" (Exodus 21:13). The chapter doesn't quote that law. It gives Solomon's reason in his own words: "the blood, which Joab shed without cause" (2:31), of "two men more righteous and better than he" (2:32).