To me it's pretty clear that you shouldn't just accept missed assignments and it's also pretty clear that RI got targetted by management for being an obstacle to them through his union activities.

Unfortunately because of the way arbitration works, it is easy and relatively risk free in theory for an ENY manager to target or direct the targetting of a particular pilot and it will never come up in discovery, which is informal at best when it does happen. I've seen this myself with how the company responded to another pilot who likes to complain excessively (imo) about hotels.