I had initially found that you can skip Marcus's dialogue by crouching on a wall by accident one day. It works because you are doing an action which stops Marcus from saying the line. However that method is no longer used in runs because jamming your pistol to skip the lines is much better. Because it doesn't require a wall to crouch on and you can do it at anytime. This new method works on all versions of the game be it unpatched or patched for Xbox 360 or the Xbox One version.

Credit Slevanas found the original dialogue glitch for 360 by crouching. Flurby improved the dialogue glitch finding out you can jam the gun to skip the lines. 5/21/2017