Here is my answer to the questions you asked:
We have an illegitimate government. The U.S. was established under the proposition that people should be ruled by laws and not the whims of a king. The Constitution was to be the supreme law of the land, our king. Our present government is in a state of rebellion against the legitimate king- the Constitution. When the government collects taxes to pursue ends that are not permitted under the Constitution, citizens are morally justified in evading those taxes by any means available.