Reply #2: Three reasons I can think of off the top of my head. [View All]

[Veritas_et_Aequitas]

1) The whole "render unto Caesar what is Caesar's and unto God what is God's". When Christ was pressed with a question similar to yours, he gave that reason to support paying taxes to the Roman government while at the same time dedicating one's life to following God's teachings. Good Christians are supposed to remain in the world without becoming corrupted by it (quite a difficult task).
2) (The more ironic reason) The Catholic Church abhors scandal. In a democratic society where tax paying is expected of its citizens, a Catholic not paying his taxes would cast a bad light on the church
3) (The more practical reason) The hierarchy simply knows that's not feasible, particularly since taxes also pay for a number of programs that the Church fundamentally (or at least should) agree with, such as social services. It would be cutting off your nose to spite your face. On the other hand, mobilizing parishioners to vote a certain way is a less risky way of achieving its goals.

Catholic political thought is fairly complicated considering it has constantly changed over the last 2000 years and has a lot of apparent contradictions in it.