Rebasing merge commit fails during --preserve-merges when ancestor merge is deleted

I have this situation and an accompanying sample repository
reproducing the issue:

https://gist.github.com/fj/7124501/raw/8d37058c1452379d0ae58bd87b0b9e0380bd80b2/gistfile1.txt

* I would like to rebase and delete a spurious ancestor merge commit
(bbd8966 in the example).

* When I do that, however, a successor merge commit (97ba1d7) that has
the ancestor merge commit (bbd8966) fails with the noted error:

=====
error: Commit 97ba1d761f60b901f56766886da4ed678e56abea is a merge but
no -m option was given. fatal: cherry-pick failed Could not pick
97ba1d761f60b901f56766886da4ed678e56abea
=====
The expected result for me is that a new merge commit that merges
6b8c765 (which now occupies the topological spot of the previous
spurious commit, bbd8966) and 11d8b92.

What am I doing wrong here? Is there a way to fix multiple instances
of this in a history without doing tedious cherry-picking?

Thanks!

~ jf