I think this quote is particularly apt. Public opinion/support is crucial to maintaining the legitimacy of any important public policy, immigration included. I'm not sure why self-styled "progressives" (or liberals, as they're often described in the U.S., where the term often has a different connotation than here in Canada) believe that immigration should be treated any differently. I suspect many of these people simply don't understand history, including the struggles of ordinary people to put in place and maintain public social security programs, like pensions and health care, to enhance and sustain their own stability. Most people are generally willing to pay relatively high taxes to support this system provided they have some assurance it will benefit them when they need it to. It's the foundation of the modern "social contract" that emerged in one form or another in all Western countries in the 20th century.
Over the past few decades the social security systems in many Western countries have been diminished and many feel public resources have been redirected to serve other purposes, including the maintenance of permanent subsidy classes. Prominent economists, including Sir Paul Collier and the late Milton Friedman, among others, have noted that open or large-scale immigration undermines social solidarity and erodes the viability of welfare or social security policies. Maintaining strong borders is crucial to sustaining both wages and social supports. Friedman preferred open borders and was willing to sacrifice the welfare system. But, as he noted, a dual policy of open borders and maintaining strong social supports is irrational and unsustainable. Our political and economic elites scoff at these concerns because they're not greatly impacted by them. But ordinary voters aren't as cavalier. And they have a right to their say as long as our countries continue to function as democracies. Contrary to the prevailing liberal/progressive view, for most voters this is not about racism. It's about maintaining the decent working conditions and social safety nets many have worked long and hard to sustain. Voters will support politicians who reflect and/or share their concerns. It's common sense.