Surely it's no different than going after smokers, banned from pubs, banned from work places, banned from some public places. If you break the rules you get fixed fines, and the publicans get bigger penalties, it's destroyed some businesses.
People can lose their jobs for smoking at work, in a non designated place or at the very least disciplined.
People in their thousands have been fined for dropping a butt on the ground, heavier fines than parking penalties for motorists and most the other litter still goes unchallenged, they purposely target smokers outside railway stations.
In fact tobacco smokers are probably the most discriminated against section of society.
So why should I accept a class A drug user, when what was my habit was restricted and banned in some places, class A drugs bring the biggest problems to society and crimes of the most violent nature.