Using leverage isn't the same thing as belonging to a corrupt union. If anything, your leverage should be used to improve said union, if you have it. The same energy and fervor that goes into establishing a union presence and and should also be used to maintain it through positions of leadership and involvement within the union.

I agree that not all unions are fantastic, but staying on the sidelines when you could use your position to influence for the betterment of everyone is a very privileged, selfish act.