Aside from Boo Radley and Tom Robinson, can Atticus Finch be considered a mockingbird?

To Kill a Mockingbird is all about
mockingbirds, even though the actual word is only mentioned three or four times in the
novel.  The reason it's a sin to kill a mockingbird is
because

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mockingbirds don't do one thing but make music
for us to enjoy.  They don't eat up people's gardens, don't nest in corncribs, they
don't do one thing but sing their hearts out for
us. 

Boo has never done
anything but try to be kind to the Finch children; he minds his own business and helps
when he can; his only sin was being born different.  Tom has never done anything but be
kind and helpful to a young woman who clearly needed help; his only sin was taking pity
on a white woman.

Atticus is not an obvious mockingbird, as
he is neither poor nor black nor an outcast.  Instead, his offense is trying to do the
right thing in the face of prejudice and hate.  For trying to right a wrong--"to make
music for us to enjoy"--he was spit on and villified, and his children were nearly
killed.  That makes him a mockingbird.