You can start by discussing things and not quibbling over terms.

> What does "defend" mean?

Keep it from being replaced by another culture. I think we all understand that.

> How can a minority "impose" its culture?

By being locally dominant. By catering to people from their own community who prefer not to join the local culture. By providing cheaper/better/more profitable things to the locals than the local culture does.

You're going to have to be more specific and maybe give some examples. I don't see a path from cheaper produce at some ethnic stores (the only part of your comment connected to reality) to total cultural replacement.