Why was Sandy fired from his job at the Westing factory in "The Westing Game"?

Although at one point Sandy complains that he "got fired for no cause" (Chapter 22), the purported reason for his dismissal is because he apparently tried to form a union.  In a conversation with his partner, J.J. Ford, Sandy straightforwardly admits to her that he "got fired from the Westing plant for trying to organize the union" (Chapter 14), and his own entry in the thumbnail sketches he keeps in his notebook about each of the heirs mentions this reason for his dismissal as well.  The entry says,

"Alexander McSouthers...Called Sandy...Worked in Westing Paper plant 20 years... Fired by Sam Westing himself for trying to organize the workers...No pension" (Chapter 21).