Scotland has an aging population and a total fertility rate of 1.25—we need *either* a TFR of 2.05 *or* immigrant labour to retain a stable population, and without a stable population we face a grim future of diminishing economic output and a rising ratio of dependents (largely elderly and infirm) to workers.
Nor can we breed our way out of this—it takes 20-odd years to manufacture a new worker that way.
@cstross This is also an argument for ubiquitous public transit; if you travel with some sample of the people around you, your "they look weird" reaction fades out.
It takes a few years, but it does, and that's important. Otherwise you get people for whom no rational analysis begins to reach their "it looks weird, kill it" responses to unfamiliar people.