How does one determine a sociological "tipping point"?  What is "a critical mass"? All questions without a precise answer, but that does not mean they are not real social phenomena.

When people arrive into a society in such large numbers and at so high a rate, that thery constitute the majority of a population in a given area, its schools, its hospitals, etc., then they find they have no mainstream culture in which to acculturate, they are the mainstream culture, and the previous inhabitants have become the minority which must adapt.

And this is somehow right and fair, and anyone who objects is "racist"?

How about everyone should have the right to feel secure in the knowledge that their home is their home, and their government is there to protect their home, not try to evict them to make way for "a better, preferred population"?