I think part of your premise is wrong.

Pain is often a precursor to self-reflection and personal change and perhaps he felt something, considered it and made a shift. While it might not be to your liking, itossing principles isn't a bad thing. If for example he was a Neo-Nazi, would you want him to stick to his principles regardless of what he felt was right?

If there is no avenue for us to change our principles, we can be no better principled than our parents teach us to be, and that is dangerous imo.