Well I can't argue with your logic because of course it would always be best to vet the people entering the country. But as you said, we have no way to know. These people are here legally, so much like our own citizens, we're kind of stuck with them, for lack of a better term. So how about we just deal with that reality? While anecdotal, I can tell you that the issues I deal with from an employment perspective are no more pronounced from that group than they are from other nationalities whether American born or not.
My opinions on this are shaped by my own experiences and interactions. I work directly with several people from this cohort, and have worked with many others in the past. Some are wonderful, hard working folks. Some are a-holes, hooligans, and thieves. I've hired them, written them up, fired them, praised them, and promoted them. They are not going anywhere, and they are now part of the fabric of the state. When I was growing up in this area, the same vitriol was directed at the Hmong immigrants. They were dog-eating, violent savages that nobody wanted or invited, and words like slant and g**k were heard more often than ni**er.
Now they're just Minnesotans.