"Self-organizing" does not mean uncontrolled
Given the team are self-organising and they are deciding to organise
away from Scrum...
I believe your development team is grossly exceeding their bounds on the pretext of "Self-organizing". To cite a small example, the stakeholders now have to wait for, say, nine months to see the first demo of the project, instead of every two weeks.
Here are a few quotes from Mike Cohn's presentation on Leading a Self-Organizing Team:
It does not mean letting people do whatever they want to do.
[Management sets the] boundary within which self-organization occurs.
From the original 1986 article by Takeuchi and Nonaka that introduced the term "Scrum":
Although project teams are largely on their own, they are not
uncontrolled. Management establishes enough checkpoints to prevent
instability, ambiguity, and tension from turning into chaos. At the
same time, management avoids the kind of rigid control that impairs
creativity and spontaneity. Instead, the emphasis is on
“self-control,” “control through peer pressure,” and “control by
love,” which collectively we call “subtle control.”
However, it is not clear why the ScrumMaster, let these concerns pile up instead of addressing them as they arose:
They articulated a number of concerns...
If I were the ScrumMaster, instead of being on the defensive, I will try to drill down into these concerns and make a serious effort to understand the root causes and look for solutions.