Your mistake is thinking a large corporation gives a single flying fuck about you as an individual employee (who's proven themselves rowdy by trying to bargain).
You aren't negotiating against the corporation. You're negotiating against the people who determine your compensation. (This is a seemingly-minor, oft-overlooked and enormously-important distinction.)
Many on this forum have leverage over those people. (Some over the corporation.) For those people, unionization could be a net negative. Recognizing that doesn't mean the idea isn't worth pursuing.