I've just snook on to VGChartz at Uni, so I haven't read the thread and I'm going to be brief.
First off, all people should be judged on their individual merit... Just sayin'.
But yes, statistically you are more likely to be a criminal if you are an illegal immigrant (where as I imagine the legal immigrant to existing population criminal ratio is roughly the same.). I think that the reason would be to do with how desperate the person is.
Desperation is one of the main causes for crime and also one of the main causes for wanting to leave a country, I don't think that it is mere coincidence that many illegals are also criminals. They are forced into committing crimes in their own country because they haven't got enough food or money, which can cause them to become thieves or dealers (or whatever else to get by). This need to provide in an environment which makes it hard would also force you to seek out a new place to go on the hope that it may be more prosperous, and this can lead to wanting to migrate illegally when legal migration isn't an option.
