How could Atticus Finch be considered both a risk taker and also an ambassador?

I love this question!  First of all, most obviously,
Atticus's willingness to be a risk-taker is clearly demonstrated when he is appointed to
defend Tom Robinson, and then makes it clear that he intends to do his best to give Tom
Robinson a good defense.  This puts him squarely at odds with most of the citizens of
Maycomb, for whom Tom Robinson's guilt is a foregone conclusion because he is black. 
Atticus's safety is threatened directly by the mob that comes to the jail where Tom
Robinson is being held; it doesn't take a lot of deep thought to infer what they have
come to do, lynch Tom Robinson.  Atticus can be thought to be an ambassador in the sense
that, as Miss Maudie points out to Scout and Jem one day, he is exactly the same person
on the street as he is within the walls of his home.  He is honest and operates with
integrity and faith in the goodness of people, almost to a fault.  His naivete about the
intentions of Bob Ewell nearly cost his children their lives, and when he makes the
decision to go along with Heck Tate to protect Arthur Radley from public scrutiny at the
novel's end, we see his "ambassador" side.  Normally unwilling to compromise the truth
for any reason, Atticus agrees to go along with the story that Bob Ewell fell on his
knife to keep "Boo" Radley's life from being disrupted in a way that would surely not be
good for him.