How you do that without being outright racist is the tough part.
And I say this as a migrated child of migrants.
What does "defend" mean?
> against immigrants imposing their cultures
How can a minority "impose" its culture?
> How you do that without being outright racist
You can start by not saying "defending" and "imposing". There's no attack. "Defending" only means enjoying and promoting all the elements of your existing culture - language, music, entertainment, food, dress, architecture, religious and other traditional celebrations.
Immigrants like to be part of the mainstream so most of them will participate, unless made to feel unwelcome, usually bringing some of their own food to the party (always a plus).
> 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.