I'm thinking we should consider create a script that finds orphaned content units in the Katello DB and deletes them. It would make solving cases like the one in this BZ much simpler, assuming it doesn't take too long.
A rake task could be appropriate.
QE Tracker for https://issues.redhat.com/browse/SAT-16260
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2172355