I might be overthinking this buuuuuut how does a deibu get a deibu badge? If you are suppose to kill them then its impossible for a person to have done it since it would be dead. So do they make it themselves or what?
There's no requirement to kill deibus, it's just more acceptable to do so.
It could be the equivalent of a bronze badge, saying "I know I own a really shitty yukkuri, pretty please don't smash it."
It could be a way to shut a deibu up if you can't or won't smash it. Give it a "badge," it shuts up/gets distracted. It's a short-sighted placating method, but whatever.
Some Anon is handing out deibu badges just for the hell of it. Find a gathering of deibus, give a few badges and watch the paste fly.
A Diebu GPS homing device inside the badge perhaps? To keep a good track of them while you are out. Helps you get them back from where they might wander [if you are inclined to do so]
I imagine the Deibu badge would probably be used for trolling purposes. Perhaps even pest control seeing as they do a good job of killing off other yukkuris.
"Reimu got the Mister Badge she always wanted! Now Reimu's a speeeecial yukkuri!" "Hey, shitty geezer! Bring Reimu sweet-sweets! Reimu's a yukkuri with a badge! She's impooortant!"