Exactly, with adults, addressing such an issue is quite delicate and requires a number of factors. The primary one probably been how "mature" is the person, especially from an emotional or mental standpoint. That said, the receiver of this bad behaviour should in no way accept or allow it because the giver is immature. Such an attitude does more harm than good. A rule of thumb for me is usually to disconnect from the person, to become indifferent, at least for the foreseeable future.
Thanks for this insightful reply!