In reality I walked away from the work, told the owner in no uncertain terms that he needs to get rid of the other developer and I refused to be responsible for the quality of the work. Fast forward to today, I'll be putting a new system in place later this week to replace the old because the owner finally called me back desperate after 6+ months of this system not working when the initial estimate was for 4 weeks.
See, the great thing about it is that I do good work. I insist on it. I've been doing good work for this guy on and off for 6+ years. I still do good work. This guy knows this. And I guarantee you, the next time I call him up and tell him one of the developers doing work for him isn't worth the time, he'll listen. Because in all the years I've done good work for him, I've only said this to him once, and time showed me to be 100% correct. Because, as it turns out, despite the fact that I don't shit sparkles, I do try to work with people until it's obvious they're not worth the effort.
Did I mention I still don't shit sparkles?