The second time you end up in the Kickstand Bar (after the murder, before you head to the Mink Ranch) there is a trucker named Emmet in the bar playing five finger fillet with a knife. If you talk to him, one option is "I can do that." He'll turn you down. There is then an option where you ask again. He'll turn you down again. Keep asking over and over and over again (something like 10-15 times) and eventually he'll actually change his response and let you do it, unlocking the achievement.