Gonna make the assumption you are young and/or new to the industry. Lots of words get tossed around. A lot of them don't have much meaning anymore. Scab has enornmous meaning. Somewhat hard to appreciate because it has been decades since anyone became a scab, certainly at a major.

Pick whatever cliche you want - scarlet letter, beyond the pale, shunned, expelled - there is simply nothing you can do, by an order of magnitude, as bad as crossing a picket line. Nothing good can come from associating yourself with someone who has, even 40 years past.