Should be humanely put down. Their photographs should be displayed on P&C and disabled parking spaces as a warning.
Thought experiment 
Declaration of interest: I'm a smoking, drinking, fat benefit claimant.
Who else should be included in the population purification programme? All immigrants, or just immigrants from certain countries/religions/phenotypes? Parents with baby backpacks? Shoppers in pyjamas? Vegans or meat-eaters?
This is Very Important!