I myself have had a couple of friends who are addicts themselves. One has been sober for over 2 years now, and the other still uses. This doesnt make them bad people. i know for a fact that both of them had horrible childhoods and this is most likely the reason they abuse substances.
I dont try to provide excuses for them to do what they do, but this doesnt make them horrible people that dont deserve to be cared about.
I cant pretend to know what it feels like to be them, all i can do is continue to be a good influence and show them that i appreciate them and love them as friends, their journey is theres to take, you simply must not enable them and reject any form of use in your presence.