Easy. There are days where I feel like staying home and drinking beer / eating junk food / playing computer games. It's only because I know that's not the right thing to do that I instead go to work and do something productive, hit the gym, help kids with homework and so on. Now granted, people can come to a stage where shame is not enough to keep them going and they need medicines, therapy and so on. But for someone lacking a moral compass in the first place, none of these things are going to work. We are biologically programmed to seek easy dopamine hits. It takes knowing that it's wrong to smoke fentanyl and get high to make use of available addiction treatment.

That's not what they said, this has to be a bad faith interpretation. Narcissistic personality disorder (NPD) for example has lack of shame as one of its defining traits.