Addiction is certainly no excuse for being a shitty human being, that's for sure.
I'm not saying that anyone is arguing the point of "addiction = an excuse to be a shitty human being"...but...I always retained at least some semblance of "right" and "wrong", even when I was at my lowest depths of depression and drug use. I've never understood the people who just completely discard all of that, honestly, and do really bad things, ostensibly because of their addiction. The people who are willing to shed all of their humanity and empathy in pursuit of a drug...I know that exists but I have a hard time wrapping my head around it. Maybe I just never got that bad into drugs, but then again I have a decent track record (no pun intended) of shooting narcotics into my bloodstream...it's pretty hard to claim "I don't have a drug problem, guys, I've got everything under control! I just like to shoot up every once in a while, no biggie!"
Whenever someone has screwed me over in a drug addiction-related way, part of me understands it a little bit but part of me also entertains the idea that the abhorrent shit they did was latent in their entire personality the whole time, and all drugs did was make it EMERGE...that's why it's hard for me to trust people ever again after I witness something very objectionable in the way they acted towards me, even if there's a plausible explanation for their actions