That doesn’t speak to other weaknesses. Substance abuse is only one of a lot of different problems that fall into the category of not behaving as well as you should and possibly suffering consequences. My contention is that if he has ever done any of those things, then he is not qualified to cast stones. Since he referenced the bible quote, remember that it is “He that is without sin among you, let him first cast a stone at her," referring to a woman who was caught in adultery. He doesn’t say “He that has never committed adultery, let him first cast a stone.” By that standard, at least, one should oneself be at least nearly perfect to throw such shade on a substance abuser.