> with the premise that immigrants are “overburdening” our social services. Most immigrants work.

I just want to point to a flaw in your reasoning.The point is not that immigrants are some special kind of human beings that require more assistance. It is just that immigration can unlike natural population growth, result in arbitrary population growth in a short amount of time.

From that view point, it makes sense that immigrants can overburden the social services, because the latter does not get a chance to accommodate the increased population properly, causing additional suffering to existing population.