Free or Guided Retrospectives

I'm a bit concerned that the Scrum Master is picking the topics. To me, this indicates a team that is being externally managed or controlled and doesn't indicate a self-organizing, self-managing team. It's one thing for the Scrum Master, ideally with input from the team, to help select formats or structures that help the team get to the root of problems, identify solutions, and plan improvements. It's a very different thing for the Scrum Master to decide on the specific conversations or what problems should be focused on.

There is a concern about a Scrum Master being able to facilitate and participate in a retrospective. There are times when the Scrum Master may want to participate, but it's very difficult to facilitate a conversation that you are participating in. For cases like this, it can be useful to have someone else facilitate. Turning to another Scrum Master, if the organization has them, is one good option, but not the only option.

How does he feel, and the team feel, about there being such a dependency upon him?

Has that ever been discussed in a Sprint Retrospective?

where he decides on one or two topics he knows the team wants to improve on or thinks that an improvement in that area would be good for the team. 

So he knows more about what is good for the team than the team does?  That sounds a lot like an old style manager and not at all like a Scrum Master. 

I think this would be a great opportunity for you as a Scrum Master to take on the responsibility you have to the organization.  Your fellow Scrum Masters are part of your organization and are not exempt from those responsibilities.  I'm sure that you have read the section of the 2020 Scrum Guide that discusses the Sprint Retrospective but it is always good to refresh your understanding. You might want to suggest that your fellow Scrum Masters also refresh their understanding as well.  I will point out a few things from that section as I feel they are pertinent to your original question.

The Scrum Team inspects how the last Sprint went with regards to individuals, interactions, processes, tools, and their Definition of Done.

The Scrum Team discusses what went well during the Sprint, what problems it encountered, and how those problems were (or were not) solved.

The Scrum Team identifies the most helpful changes to improve its effectiveness. The most impactful improvements are addressed as soon as possible

Notice how all 3 of those statements begin with "The Scrum Team" and not "The Scrum Master"?  In fact the term "Scrum Master" does not appear at all in that section and neither does "Product Owner" or "Developers".  It is an event for collaboration, introspection, and adaption.

Thank you for your answers.

@Thomas Owens: I think that's a good idea to let him participate in the retro as a member of the scrum team and let someone else facilitate the meeting. That way he can talk about those topics that concern him and the team has the chance to talk about it if they like to, but also not to.

@Ian Mitchell: He thinks he's doing something good for the team, by talking about topics the team isn't ware of or are too unpleasant. His words, not mine. I don't really know how his team feels about it but for what I know most of the topics are real concerns, so the team is fine talking about them, but still there might be more important topics that don't get addressed this way. This is my biggest concern of not having a free retro format. I don't think this was discussed internally yet.

@Daniel Wilhite:: Exactly. The team knows best what problems they encountered and what improvements they want to focus on in the near future. If those topics are so important as he thinks they are, they will be addressed sooner or later anyway.

If you join a team as a Scrum Master, listen to the impediments and look how they are doing in their daily work, you might see the issue while the team does not see it because of historical blindness. So asking the team from time to time about a specific topic and set the focus for the retro on that can be a valid approach. 

Don't get me wrong, the topics for these guided retros needs to come from the team. Some topics needs more discussion than other and why not set a big topic to discuss? Or is it better to have this topic discussion in an own meeting?

How do you handle topics where you are affected as a Scrum Master and you facilitate?

I don't have any arguments against discussing a big topic in a Retrospective, neither against facilitating this with a proper format, if this topic comes from the team itself and not only from the Scrum Master. I also agree with you about the fact that the Scrum Master should also address topics the team might not be aware of, but the team should decide if this really is an impediment worth solving or not.

How do you handle topics where you are affected as a Scrum Master and you facilitate?

Maybe you shouldn't facilitate in this case, if there is the option to get another person to facilitate for this specific occasion?

I think that's a good idea to let him participate in the retro as a member of the scrum team and let someone else facilitate the meeting. That way he can talk about those topics that concern him and the team has the chance to talk about it if they like to, but also not to.

This is definitely a good idea and approach. I tend to recommend that teams do this every few Sprints, depending on how long their Sprints are. Bringing in someone from outside the team to facilitate can allow the Scrum Master to participate in the Sprint Retrospective without dominating the conversation or using "facilitation" techniques to drive the conversation in a particular direction.

I would make sure that the team accepts whoever is asked to facilitate the retrospective, though. The team needs to be comfortable having open, honest conversations about problems and that can be hard if the team doesn't have a good relationship with whoever is asked to facilitate.