So, I had a bug today in my application. It wasn't configured correctly and it triggered a fault in another system that caused that system to start outputing invalid results about once a second. The invalid results triggered a rejecting reaction in my application, which was considered invalid by the second application, and so on.
So, after I fix the bug, I tell the person responsible that they should take an action to reject the invalid action on my system should it happen again. The action is marked "invalid", and it is something that will only go his way because something very wrong happened (but it must happen, since otherwise the app will swallow the error and no one will know about it).
His response is: "That is not an applicative concern. If you application would work right, there is nothing to worry about."
Me: "We took down production for two days because we couldn't find what the issue was because there were too many issues."
Him: "I don't want to taint my application with stuff that is not a business concern."
I am all for focusing on the domain, but that is pushing it.