Again it comes down to what is an acceptable, for lack of a better term "error rate". You may well be right that most are not that way. Yet most could be 55% or 95% that aren't that way and there is a huge difference. If it's even 25% or 15% "bad" then it's a problem in the subset of people we cannot possibly vet because the government there, to your point earlier, is essentially non functioning in that way.
Similar to the argument over refugees from Afghanistan being admitted into this country we have no way to know. And even if you are correct in your assertion and usage of the term "most" of them aren't that way, you have no way to determine in a group who those people are, and they apparently exist in too large of proportions IMO to justify taking in more people who behave that way. I'm sure that's where we will disagree. It's also a function of where people came from that they accept these types of behaviors even if they don't engage in them because it's the way they were trained in life. That may not be their fault, but it's a problem we don't need here and we are importing security threats to our country.
To me, the questions on people from Somalia, Afghanistan, etc is a different one to the illegal immigration from Mexico and Central America.