No he means Romanians.
Since Romania joined the EU, the borders are open, so Romanians have emigrated to the big Western European cities.
When they arrive, they happen to be among the most recently arrived and therefore the poorest (because no job and no right to unemployment benefits yet), and that is usually a situation that incentivises petty crime. Many in this situation would never do it, but a few do it a lot, and that’s no matter where they are from, it is based on the lack of any other option/ opportunity.