The pro-immigration argument that everyone hates

Fortunately people hate it because it is wrong, otherwise they would have to hate it for less intellectually honest reasons.  The basic context of course is that native rates of fertility are in irreversible decline.  Here goes:

Immigration is not going so well today in terms of assimilation.  Yet in the future it will go worse yet, because the native-borns will be smaller in number and also older and less energetic.  Nonetheless we need to take in a lot of immigrants today, as a kind of practice, so we can get used to the much greater number of immigrants we will need to take in a generation or two from now.  It is better to be a crummy country than a country of 33,000 people.  And so we must become crummier now, so that later on our rise in crumminess is modestly tempered, though it still will happen.  Open the gates!

See?