Alright, let's see if I can explain this concisely. I could explain this much better if we were talking face to face because I am an absolutely awful writer.
So, I was a part of the ALPA organizing drive at CAL/CALEX in 2000/2001. Before I go further first I need to give some background. 1983 there was a strike at CAL. In 1985 ALPA was busted by Lorenzo. ALL CAL pilots were scabs until the Order and Award that happened in the late 80's when the Full Term Strikers were brought back on property. That entailed a very messy senority integration.
The minute after the Order and Award the Full Term Strikers were trying to bring ALPA back on property but, they were outnumbered by scabs. Well, eventually even the scabs realized that Lorenzo was not their friend. They began to think that the Strikers might know what they are talking about and maybe a Union is needed. They tried to bring ALPA back but a large contingent of scabs did not want them so, the CAL pilots did the only thing they could do. They started the IACP (Independant Assoc of CAL Pilots) in 1993.
So, when the IACP was formed ALL CAL pilots were members in good standing (of course). So, it is now 2000 and those Strikers and now the CALEX pilots (who were also part of IACP) want ALPA on property. To do that they needed a vote of ALL MEMBERS IN GOOD STANDING (that means everyone). If the scabs were not allowed to join ALPA then they were certain to vote NO. So, they had to be "forgiven" in order for the greater good. At the time there were 900 scabs out of 3500 CAL pilots and 1500 CALEX pilots. The final vote was 67% in favor of ALPA. They tended to vote in a block and they had many sympathizers. So, they could not just be out-voted.
It is far more complicated than that but, that is as simple as I can make it.