Why does doing something illegal, addictive and dangerous only on certain days of the week make it OK?
If I say I like to run over stray animals with my car, but I only do it on weekends, would that mean I didn't have a problem, or would it mean that I was justifying my sickness so that I could continue the unhealthy behavior?
Addicts use all kinds of rationalizations to justify themselves. Mostly for their own edification, but if they can get someone else to buy their bs, then that's just gravy.