And, AOG, rereading you post, it really is what you believe. You should be gratified that there are black on black stabbings. Each killing means that there is one less black here, which should suit your views admirably. You should take the sanguine view of the police in Nice, who greet each shooting of one gangster by another as "a settling of accounts" , and give a gallic shrug while putting the papers at the bottom of the files.
Organised crime does cross borders. It does not matter whether it is British drug dealers or Eastern European pimps, they trade where the money is.
Locally, the criminals will fill the criminal jobs which are available. I can remember the Mifsuds being pimps on a large scale, being big players in the vice trade in Soho. They were Maltese. But the same business was available to British natives, and was pursued by them. So, be it Polish plumbers or Latvian fruit pickers, if the jobs aren't being taken by natives, foreigners will do them.