I think you give way too much credit to leftists.
Situational ethics, moral relativism, and systematic hypocrisy are absolutely necessary to their paradigm.
Please do not imagine me to be saying that what I describe is a rational process, for many it is not.
They hear scandal about “progressives” and they circle the proverbial wagons. They don’t have to think about doing so ... they just do so, especially if the source of the complaint is a conservative or any Republican.
Likewise what determines if they cease to actively resist the idea of wrongdoing by “progressives” is not necessarily rooted in reason but likewise in their emotions. If it, whatever it is, is only about as bad as things they couldn’t bring themselves to care about before they are highly unlikely to care about this new thing now.
Even what needs to happen to them to get them to stop resisting, managing to care, is itself an emotional change.
Only when their emotions are out of the way, when the we vs they has ceased to resist, does reason tend to takeover. If it does engage at all of course (some folks can go straight from resisting the suggestion of wrongdoing to outright rage about wrongdoing without really drawing upon reason ... this may well be why it seems like even if you can get a “progressive” to care deeply about one thing the very next that they may not care about something else ... emotions do not establish principals that they can apply in all such instances and, also, it’s hard to be jacked up on emotions all the time ... they will eventually crash and with that cease to care as much).