Abishai asked this question to express his anger at the man. This rhetorical question can be translated as a statement. AT: "This dead dog must not speak to the king this way." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Here the man is being described as worthless by being compared to a dead dog. AT: "this worthless man" (See: [[rc://en/ta/man/translate/figs-metaphor]])