Of course they do.
They (let's be vague here) actually are doing it for that very reason. If you can break the cohesion of any group you make it harder for the people to resist you.
You break cohesion by introducing outsiders in large numbers, especially ones that do not speak the same language or have the same religious customs or by breaking the institutions that get these people together and re-enforce societal bonds, large extended families, churches, clubs, civic groups anything like that.
I think you both missed the “not” in the sentence.