I've had a copy of the "Master Scab List" for a while, and I've done a bit of research on it. Long story short, many of the people on the list belong there. Others do not. Parts of the list have been cobbled together from a series of word-of-mouth rumor chains years after the fact, and the list is not officially sanctioned by ALPA or any other union. There is no union signoff on this list, and the website and contact email given on the .pdf file do not exist.
Some people ended up on that list for reasons that are apocryphal at best, and malicious at worst. As an example from my personal experience, I have had extensive dealings with two former Eastern pilots whose names appear on the list. They have both proven, to the satisfaction of myself, their current unions, and their co-workers (some of whom are former Eastern pilots who do NOT appear on the list) that they didn't scab for Lorenzo, and made great personal sacrifices to avoid doing so. They haven't a clue how they got on the list in the first place, and no procedure exists for getting names removed from it. Needless to say, their presence on the list has damaged their careers, and caused them no small amount of personal grief.
But as I said, that's just one example from my own experience. For another discussion of the questionable nature of this list, and of a pilot on the list who disputes his place there, please follow this link:
http://unfactualbias.com/wordpress/?p=242. The examples I've referenced are by no means the only ones.
The label of "Scab" carries more weight than most people can know. People in this industry, especially some of you FI keyboard warriors, would do well to remember that before throwing it around so lightly.