With a country as large as this one, you could cherry-pick examples to make the case that pretty much any sizable group you care to name is a huge problem. If I wanted to collect examples of guys named "Joe" who have committed murders and other heinous crimes, I could find thousands of them, and find a steady stream of new ones every month. Similarly, I could smear left-handed people, red-heads, Baptists, Hoosiers, veterans, clergy, married women, or any other large group, simply by using the consequences of large numbers to feed the fearful a steady stream of anecdotes. Undocumented immigrants are no different. There are enough of them that it's inevitable some will do terrible things. But, if you look at it statistically, it turns out that undocumented immigrants commit serious crimes at lower rates than native-born people. They make America safer, not more dangerous. Of course, understanding that point means liberating oneself from xenophobia enough to think clearly. Fear is the mind killer.