Hi Sadness. Glad to hear you're getting to communicate with your dad. He's probably right... HIS actions would have gotten him there eventually with or without the stepmom. So he is being honest and accepting responsibility for his actions. That's a good start to hopefully working on recovery.
I think the 3 C's of addiction kind of apply to the situation with your friends...
1. You didn't Cause it
2. You can't Control it
3. You can't Cure it
You only have control over yourself. You can't control what your parents choose to do or not do. No one is responsible for another persons choices. Try to remember, other people don't define you. You are your own person. I know its hard, but try not to let what uninformed people say bother you. They just don't know all the facts and sometimes say crazy things.