It's a crime

I'm a bit puzzled by one aspect of this foreign criminals business that's been in the news lately. Clearly it's pretty incompetent to not know what on earth is going on with them, and to not be able to deport those whom the judge has said should be deported. But the press has been dwelling not on that but instead on the horror of VIOLENT FOREIGN THUGS STALK THE STREETS -- and not just the tabloids. What I don't understand is, given that there are thousands of criminals wandering around having served their sentence and been let out -- that being the nature of sentences -- why is it so much worse that some of them are foreign? Why should they be deported after release, if the judge thought that the sentence handed down was sufficient punishment for their crime? If only 5 out of 1000+ have reoffended, that sounds like their recidivism rate is actually less than the native population. Or is the subtext that really people aren't happy about anyone who's committed an offence ever being let out of jail?