Imagine, you are a Leaf Ninja. Your village is undoubtedly the strongest, keeping evil Mist in check until the next time you have to put them down.
Imagine, Jiraiya of the Sannin starts a clan with "former" Mist Ninja that have somehow gained Jiraiya's trust. Jiraiya must have been thinking with the wrong head when he engaged Mari the Heartbreaker.
In fact, the "former" Mist Ninja that Jiraiya made a new clan with only have strength in that same Heartbreaker. Two middling sealmasters, and the younger three members are all the dredges of their "former" clans. Weak.
Imagine, Jiraiya has died. "Goketsu", Mist in all but name, remain in Leaf. Now they send their "former" Mist Jonin to try to take the Hat‽ This blatant level of disregard for Leaf's strength, coupled with what is very clearly a bluff of strength on their part, only demonstrates an incompetence on Mist's part. And by moving like this, they have finally allowed loyal Leaf Ninja to remove them!