Holding them to the highest standard and having a discussion is fine. Bringing up non applicable points from the past is not ok. The premise being made in that argument was "mark was untrustworthy as a student and therefore he should be treated with suspicion now". That premise is flawed as it has no logical connection to the present. If someone can bring proof that Mark still doesn't care about privacy and is cavalier about it, fine. That point doesn't do that. Therefore, it shouldn't be part of the discussion.