A detective story without a dash of violence for flavor would be pretty bland, and The Big Sleep is definitely not lacking in the spicy action department. Fistfights, shootouts, bloody corpses—all the bases are covered. In the end, we realize that violence is the inevitable result of the total moral depravity going on in society. These tough guys only have a few options when it comes to getting their way, and violence is often their method of choice.
Violence isn't only a man thing in The Big Sleep. Carmen has proven herself to be just as violent as all the tough guys.
Marlowe's use of violence during his own investigation shows that his high-minded principles are really just a bunch of codswallop. He's no different than the rest of the tough guys.