Here's the tough question: Does our docile compliance with unjust authority spring from a good conscience, or from fear of reprisal? 232 years ago, certain Loyalists felt conscience bound to obey King George. Perhaps some were simply afraid to disobey. In either case, there would never have been an American Revolution had their voices prevailed. Likewise, had the Apostles felt obliged to obey the authorities, they would not have proclaimed the Gospel (Acts 4:18). True obedience can sometimes look like rebellion.
It isn't nearly as complicated as we might pretend. Difficult, yes. Unpleasant, to be sure. But not complicated. To subsidize a crime is to partake in the crime. Abortion is a crime. To willingly pay for it is to share the guilt. If you agree that abortion is the taking of an innocent person's life and the maiming of another's, then you really need to stop supporting it. It's the Law.