GM, I have wondered at times if my xh always had a personality disorder Now however, after reading and researching it (not as much as you) I believe that many people who exhibit MLC behaviour maybe had it latently
My xh truly was a nice and kind man and a good father for many years. He could be difficult, and exhibit passive aggressive behaviour, although this is a learned pattern from both of his parents, but overall, not the man he has become.
I do agree however, that a proportion of LBS come to see that the behaviour was always there, that they are the latest 'victims' of this pattern.
However, I do think that the roots of personality disorder, like MLC are laid in early childhood, and become increasingly evident, unless the person is able to seek and receive appropriate help. Jekyll and Hyde describes it perfectly. Perhaps the true sociopath is better at concealing the 'Mr Hyde' aspects. With the MLCer it is evident to all.
In either case, MLC or on-going personalty disorder, we need to protect ourself and our assets, and most of all, the emotional well being of our children.