Is large scale immigration good or bad?

Immigration on a large scale is counterproductive for the citizens of a country and for the immigrants themselves. It places too much strain on public resources, such as housing, schools, medical care, law enforcement and so forth. It's not so much a matter of whether large scale immigration is good or bad, but whether they are the people we want in the country. Have we been able to determine if they are criminals? Do they have a skill that will help the country? Are they able to provide for themselves and pay for their own medical expenses? There are plenty of reasons to allow immigrants into the country, especially since most of us are decendants of immigrants. Immigration is not a bad thing in any way, it's just when it is no longer controlled and when you have to start questioning the motivation of the immigrants.