Let's be clear about this. It was ALPA as a whole who collectively changed the merger policy. Regardless of who put the idea on the table, ALPA is still a democratic organization and it was voted on by all.
I know this idea is contrary to the belief system of the US East pilots, but ALPA does not revolve around them. They are not the only voice, nor are they the largest or most important voice within ALPA. They are actually relatively insignificant when compared to the collective voice of all pilots represented by ALPA National.
No one group has the power to change anything. UA could not unilaterally change policy any more than US can unilaterally change it back now. As the EAST pilots love to point out to the WEST, whoever has the most votes will prevail. Unfortunately in their self-centered world, they can not understand that it works both ways. That same rule does not just apply to them when it works to their advantage, only to be disregarded when it does not.