It is the legitimacy of such government, and indeed taxes, which merits careful consideration.
One of the things that severely degrades the legitimacy of our government is the lack of standing you and I have, by default; in short, I cannot challenge a law as contra-constitutional unless I first break the law and then defend myself in court as the accused -- this makes my challenge dependent on the implicit acknowledgment of that law's authority and therefore legitimacy. Another thing that indicates our government's illegitimacy is, as Waco showed,the readiness and willingness for the wholesale slaughter of the accused, and the refusal to investigate/punish those who participated in said slaughter. Fast & Furious completely illustrates this point in that it is (a) State sponsored terrorism, (b) unauthorized acts of war, (c) accessory to [another] slaughter, (d) Treason... and yet the government has done all of nothing in pursuing justice.
All governments pursue a limited number of the charges that can be pursued. That our government like all other governments also pursues a limited number of cases does not make it illegitimate.
There is no power given to the federal government to use terrorism. Acts of terrorism committed by federal executive officials are not those of the government, but rather those of the executive officials, individually or severally. That is why those officials can be prosecuted. Such acts do not impact or affect the legitimacy of the federal government.
By contrast, illegal acts by a state government, passed by the legislature, and ratified by the governor can remove legitimacy from the state government. Illegal acts passed by a convention of the people, elected for that purpose, can do the same thing.
Of course court cases only resolve controversies that exist, rather than cruise about looking for trouble.
There is one law, the 1867 anti-injunction act which forbids court cases contesting the validity of tax law until the tax has been paid. The recent Roberts decision had to hold that the Obamacare law assertion that it was a penalty, not a tax permitted the court to handle the case, or else some schmuck would have had to either pay the tax and then sue, or would have to not pay the tax, and then be prosecuted by the IRS.
That several state attorneys general had filed suit against the US, requesting resolution stood in their favor, and against your assertion that you have to break the law and then defend yourself in court.
Even if you did have to defend yourself against an unconstitutional law, what of it? If you feel sure of your position, and it has not previously been ruled upon, then you should not feel oppressed by that. The alternative is to have no law at all, and others could use that to oppress you, and in that case you would have no recourse. The smallest minority is the individual, and court procedures offer the greatest protection of individual rights, compared to majority votes in the legislature, or a single person defending against a mob.