I talk a lot about facilitating self-organizing teams. For a Scrum Master, a little more than facilitation skills and authority for the process is needed to ensure people interact with professionalism and demonstrate the right behaviors - respect, humility, empathy - at all times.
In most organizations, a Scrum Master is actually a manager and, sometimes, a Scrum Master has to step in when people misbehave, but the objective is really to help a team manage itself. The challenge for a Scrum Master is to develop a demeanor that hints at authority just enough to keep people true while giving them freedom. The question is how does someone develop such a demeanor?
I think what you say and how you say it plays a part. As does what you do and how you do it. But you are the core. By that I mean you act by your values and are guided by your principles. And what drives you as a person determines the style in which you conduct yourself. This is what people see.

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I agree with what you write, but I think it is alos important to think about the phase where the team is in.
Every team has phases is goes through, just like humans do.
I wrote about that about a year ago.
http://paircoaching.wordpress.com/2007/09/18/how-to-grow-a-self-organizing-team/