The Scrum Master has to lead the adoption of Scrum in the organization and, among the forms to serve the organization, the SM must help to understand Scrum and how to interact with the different members of a Scrum Team. Specifically here it must be clear that the decisions of PO must be respected.
The PO is accountable for explaining to stakeholders the PB and forecasting when the team could complete certain features or which features could be completed for a fixed date.
It seems to me that a change of mentality and create a framework of trust is necessary. A great opportunity is the Sprint Review, in which the PO can invite stakeholders and tell them what has been done and what has not, answer questions about the product increment, check the prodcut backlog, the forecast, the budget, etc.