This sounds very similar to the argument against atheism where the believer is afraid that he might start to do a whole bunch of horrible things if he’ll no longer fear punishment from God.
What I’ve noticed in my case is that yes, I now do think I could feel like a good person even if I do bad things to others. However, I now genuinely don’t want to hurt other people. In a way it feels like this is the first time in my life where I’m actually able to really care for and empathise with other people since I no longer have to be so preoccupied with myself.
I’m a member of his group so I’ve gotten personal assistance but what I’ve done is basically first diagnose my problems by using his so called RMI technique, which I’m pretty sure he’s mentioned several times here in the comments, which basically just consists of sincerely questioning yourself about your problem and passively notice what comes to mind without trying to rationalize it away logically.
Through that technique I found out that I’ve unconsciously judged all my decisions in life for “goodness”, that is I’ve constantly feared that I’ll not be a good person if I make the wrong decisions. Unfortunately the number of rules for things which make me a bad person have been very large so I’ve basically lived a passive lonely life waiting for someone to come and tell me what to do. One particularly frustrating thing has been that I’ve felt that I’m a bad person if I actually try to take control over my life, and that includes using PJs methods, so for about six months I’ve been completely clear on what my problem is, how to solve it, believed that it would work on a rational level, but at the same time feeling completely uninterested in actually doing anything about it. The trigger for action was when my girlfriend broke up with me and I temporarily got into an emotional state where I felt that I had nothing to lose, and since I knew PJs techniques I managed to use the opportunity to break the deadlock.
The specific technique I used is his so called “rights work”, which I also think he’s mentioned here. You basically tell yourself that you have the right to feel feeling X even if condition Y is true. The big one for me was when I hit upon the phrase: “I have the right to feel like a good person no matter what I do.”
Realising that instantly made me start to cry what can best be described as tears of joy mixed up with some anger and indignation. Then after a couple of minutes it was over and now I feel like a completely different person. Or rather closer to the person I’ve always wanted to be but never felt I’ve been allowed to be. For example, writing this answer has been trivial whereas I’ve previously been a chronic lurker on all forums I frequent due to worrying about what everyone will think of my writings.