A bunch of illiterate savaged made their way to My homeland and now they are asking for independence. How do I remove them?

So I am playing as Germany and some stone age people from africa with zero acceptance in the country, have immigrated to west prussia. I am not even sure why did they move there. Yeah sure they are my colony, but why can't they stay in their own home? Now they are trying to secede.

Is there any way to remove them?