It was just a jovial variation on casus belli, like calling you dictum fanaticus or something. You get my drift?
Is it a real phrase? - Is now, eh.
Is it at least grammatically correct? - I dunno.

You see Wordster, I was with 'casus dictum' trying to make the point, that often only when one becomes a tad hot under the collar about a certain topic, does it generally provoke people to speak plainly about it. A hostile start to a conversation often yields the most insightful discussions, in my eyes.