Commentary Help

What is the "so what factor" in this passage and how would I word it into a sentence

"Out, damned spot! Out, I say!—One, two. Why, then, ’tis time to do ’t. Hell is murky! Fie, my lord, fie! A soldier, and afeard? What need we fear who knows it, when none can \call our power to account?Yet who would have thought the old man to have had so much blood in him" (3.1.46-65) Lady Macbeth