Boom -- I got it.
I used helm's emacs-helm.sh and got to the "minimal" config necessary
to run helm. The org-set-tags-command worked correctly when running
in the minimal config.
I moved some initialization code from my org-mode-config.org file
to my init.el file and I got helm to work with
Hello all,
I would like to use helm to select tags for my headings,
and I'm having a tough time getting something to work.
I would like the following behavior:
1) org-set-tags-command would show a list of all tags
in my agenda files using the helm interface
2) I could set one tag for each call