It is always the right time to get your Dubs to defend behaviours that their suppressed non-cult personalities abhor.
As with any topic, you have to ensure that they don't get to decide what they are defending. They are slippery buggers and are just as dishonest with themselves as they are with you, so take care that they are actually confronting the facts of the case and not just playing toy soldiers with their usual army of strawmen.