Social contract philosophy has always tried to add in clauses that allow for non-signatories or just relies on implied consent, but the idea of how to react to a truly concious rejection of the contract has never (to my knowldge) been really been formulated. That being said, yes, the government is coercive. Its just not automatically a bad thing. Barring the fact that the analogy put forward in the original post is horribly hyperbolic and one-sided, these things are done generally for the collective greater good.
In response to Sicarius's original point of how government transforms crimes into benefits, I would begin by arguing that taxation is not theft, conscription is not slavery, and war is not murder. The entire point of government (at least in most political philosophies, including the one underpinning western liberal democracies) is to provide for the people that which the private sector would or could not in order to benefit all citizens. Addressing for now taxation, let us look at the classic example of roads. Roads are good. If anyone disagrees with this, then I believe we have much bigger problems on our hands. Because roads provide such a huge benefit to all aspects of society, they should exist. However, modern roads are not simple trails, but require huge amounts of money and labor in order to function. If the duty of road construction were left to the private sector, one could expect roads to exist only where a profit could be made by charging for their use, and even then it would be the right of the private road company to charge what they wish, which, depending on the efficiency of any particular company, could be far more than what the poorest level of society could afford. Costs would also increase due to the requirement of policing these roads to ensure that only those who have paid to use them are doing so. There could also be redundency in infrastructure, as two competing road companies attempt to take over an unclaimed territory (the benefits of a government monopoly in order to avoid redundent infrastructure can be seen more clearly in public ulities). This does not paint an appealing picture of private control over road construction and maintenance. Given that the private sector would be unwilling or unable to adequately provide this necessary service to all people of a nation, it is the duty of the government to do so. But this still requires money that has to come from somewhere. Returning to our previous assumption that roads are good and benefit all aspects of a society, it is not unreasonable to conclude that all of society should help pay for roads. Taxation, then, is one way of charging for a service that is being provided, because it is assumed that everyone in a nation is either using this service or is benefiting from it, and it is easier to charge a blanket tax than to attempt to charge people for public services as they are used.
It is this principle which can be used to explain the other two crimes that have been thrust onto government in this thread, conscription and war. It is assumed that, by virtue of being a citizen of a country, one has a desire to live in that country. If not, they would be living somewhere else. This country must be defended from those who would harm it or its vital interests. This requires soldiers (as well as money) who, in dire times, may be drafted to fight a war for the nation's survival. Drafting is, of course, coercive, with huge penalties for avoiding when it is asked, but to live in a country that has the potential for emergency conscription (and while living there enjoying all of the legal and civil protections provided as well as the public utility services) and then to dodge a draft is to run out of a restaurant without paying. In order to get out of civil obligations like paying taxes and signing up for selective service, one would have to completely abandon civil benefits, which include, among other things, infrastructure, a police and judicial system, and currency. Like it or not, every second of every day the government is providing a multitude of services to every citizen (and here I would like to remind everyone that I am speaking of western liberal democracies; the merits or totalitarian regimes are a different subject). These services are generally assumed to be in the greatest good of the most people, and since choosing not to receive them is not an option due to the inefficiencies and legal complexities it would involve, it is therefore not possible to choose not to pay for them.
This is most certainly coercive under at least some definitions of the word, but not totally due to the nature of a western liberal democracy. What constitutes the greatest good of the most people is determined through elections. One could make a valid argument that a country like the United States is too large to be governed effectively and that more power should therefore be delegated to the states in order to determine what the people want, but the simple fact is that under any democracy a majority (or plurality) of people is capable of suppressing the minority in order to get its way. Opinions obviously change over time and the majority one year could be the minority the next, but it is the duty of the minority to argue their points and to drive for compromise, confident that if they are truly correct then their desires will be fulfilled in time, but knowledgeable of the fact that they may not be supporting that which the people truly want. If members of the minority do not feel that they are capable of living under the dictatorship of the majority, then their only option is to flee the country. Safeguards are installed in constitutions in order to avoid the dictatorship of the majority becoming a dictatorship of one, but the only way to rationalize a system that does not favor the opinion of the majority is to value the opinions of some people more than others, which is not a principle held by modern liberal democracies.
I don't normally post on these threads, but this particular topic is very close to my specialty and I simply couldn't resist myself. I hope I have at least made the case for the other side worth thinking about.