Peoples, People, Nation
The mouth clan are a group of people. They are the people of a nation.
The mouth clan are distinct peoples. They do, of course, use their mouths.
みん
たみ
None
The mouth clan peoples are a nation of people who use their mouths to say mean (みん) things to other peoples.
That's why they're the mouth clan. This nation of people are known for mouthing off and saying mean things. Imagine them, as a nation, saying mean things to you. How awful! All being from the same place, they're all into it too. In a way, they're not the mouth clan, they're the mean clan.