I was thinking at the back of my mind to either:
- defend the PO and budget
- defend the team, since they were kept busy delivering items from the backlog
- Bring focus to the meeting by telling POs to keep focus on delivering high value items in the following sprints
The correct answer is "none of the above." Your goal as Scrum Master isn't to defend anything except the process. A good Scrum Master acts as a coach, an educator, and (when necessary) a process referee.
The problem you're describing is one that often results from poor process transparency, or from a product/portfolio management methodology that lacks rigor, objective metrics, and (most importantly) stakeholder buy-in. There are a number of existing approaches for dealing with that, which I addressed in a previous answer.
Below, I offer a process perspective and an interpersonal perspective on what the problems may be. I also offer some practical suggestions on how to address them within the role of Scrum Master.
The Process Perspective
From a process perspective, a Scrum Product Owner is responsible for managing the Product Backlog. In practice, this often means managing stakeholder expectations about how priorities are being set and (indirectly) how project budget is being allocated.
There are a number of techniques for getting buy-in for prioritization and budget, but they all ultimately boil down to good communications and selecting metrics everyone can agree on. If stakeholders are not already on board with the Product Owner's priorities, or if the project sponsor isn't backing the budgeting process effectively, then this is certainly an area where a good Scrum Master or agile coach can facilitate communications and help the organization to collaborate on budgets and priorities more effectively.
The Interpersonal Perspective
While it's not your job to defend the budget or the Product Backlog priorities, there are some interpersonal techniques that can make it easier to defuse this sort of unproductive meeting. In general:
- Don't get defensive or pick sides.
- Capture any concerns or objections raised by the people in the meeting.
- Be willing to (politely) observe that the meeting has created action items for the participants, and that it may be time to adjourn to consider them.
- Discuss the meeting with the Product Owner afterwards, and work together to evaluate alternative approaches.
- If welcomed by the Product Owner and the stakeholders, offer to coach the organization on agile prioritization and budgeting techniques.
- Suggest hiring an agile coach or consultant if the process is so far off the rails that it endangers the effectiveness of the project.
In all cases, your goal is to facilitate communication, not defend or change the current process. As long as you're continuously improving team and organizational communication, visibility, and transparency, then you're fulfilling the Scrum Master role properly.