Mariology is one of the worst IMO and full of error.
When you come out of a group, you may feel you have authority to speak on some of the issues discussed in that group.
That way you can demonstrate to observers that you are obsessed with it and have an ongoing need to have your decisions validated in the eyes of others.
I know plenty of ex-Protestant Catholics. None of them seem to feel a need to paint themselves as authorities on Protestant belief, whether in front of Catholics or Protestants -- even though some of them legitimately could claim to be.