I’d be inclined to give United some leeway in the way they prioritize crew members over passengers. There is absolutely no financial or customer service advantage for United to bump paying customers in favor of non-paying crew members, so I would have to assume that their method of transporting crew members is written into some kind of labor agreement.
United is supposed to be in the business of flying paying passengers, not their own crew. Transporting their own crew without disrupting schedules of any paying passenger is or should be a part of the cost of doing business, not a priority over the needs of and contractual obligations to paying passengers.
Why? Their priority is supposed to be paying customers. In this case it was already seated passengers on a sold out flight. If customers really came first they would've (1) rented a car or small charter plane for the employees or (2) booked them on another airline.
The point here is that NO ONE, except a lot of other passengers, gave a damn about passengers.
We've become slaves to the corporate elite. This shows that even paying for something doesn't assure that consumers are any more than an inconvenient nuisance in their decision making.