Taxation is not always analogous to theft nor is it correct to say it is never theft. How can we distinguish a legitimate government service that could not be performed voluntarily from a robbery at the hands of the majority? 

It would be wrong to argue that taxation is theft. It is also very naive to argue that taxation is never theft. The error comes when we view government as anything more than an abstract collection of people.  When the government becomes a separate entity from ourselves, we allow it to develop its own set of moral actions.

Certainly, it is wrong for me to take the possessions of another person. It is actually wrong for me to covet

the possessions of another person. If the state is simply the people, the administrative will of the people, then under what conditions can they take from the people?

There are two categories under which the state takes the fruits of the labors of it's people. The first is where the government provides some service that (because of extenuating circumstances) cannot be voluntarily performed by a free market. Examples of this may be the military defense (emphasis on defense) of the nation. We cannot allow people to opt out of our defense. This does not mean that any action of the military can be called defense. Another example may be infrastructure or perhaps police departments. Prisons may be an example where the free market desire for more customers may cause more harm than good. Some of these are debatable.

The other category of taxation is the use of the law to take from one segment of the population and give to another. I have heard it said that a wide disparity is reason enough for taking from one and giving to another. The 1% and the 99%. Outside of the obvious fact that what is taken from the 1% is never actually handed out to the 99%, we have another problem. Disparity itself is not a moral grounds for theft. If it was then the command, "Do not covet" has no meaning. If the government is simply an abstract collection of individuals then this is tantamount to institutionalized covetousness followed by legal plunder.

Consider 10 people living on an Island. Can 7 of them vote away the property of the other 3? What if the Island has 300 million people? Did the plunder of the minority at the hands of majority become legitimate because of the institutions constructed by those that plunder? Does the will of the majority provide moral justification to the labor of the minority?

Frederic Bastiat, in The Law answers that very question when he defines Legal Plunder. "Sometimes the law defends plunder and participates in it. Thus the beneficiaries are spared the shame, danger, and scruple which their acts would otherwise involve. Sometimes the law places the whole apparatus of judges, police, prisons, and gendarmes at the service of the plunderers, and treats the victim — when he defends himself — as a criminal. In short, there is a legal plunder...

But how is this legal plunder to be identified? Quite simply. See if the law takes from some persons what belongs to them, and gives it to other persons to whom it does not belong. See if the law benefits one citizen at the expense of another by doing what the citizen himself cannot do without committing a crime.

Then abolish this law without delay, for it is not only an evil itself, but also it is a fertile source for further evils because it invites reprisals. If such a law — which may be an isolated case — is not abolished immediately, it will spread, multiply, and develop into a system.

The person who profits from this law will complain bitterly, defending his acquired rights. He will claim that the state is obligated to protect and encourage his particular industry; that this procedure enriches the state because the protected industry is thus able to spend more and to pay higher wages to the poor workingmen.

Do not listen to this sophistry by vested interests. The acceptance of these arguments will build legal plunder into a whole system. In fact, this has already occurred. The present-day delusion is an attempt to enrich everyone at the expense of everyone else; to make plunder universal under the pretense of organizing it.

Now, legal plunder can be committed in an infinite number of ways. Thus we have an infinite number of plans for organizing it: tariffs, protection, benefits, subsidies, encouragements, progressive taxation, public schools, guaranteed jobs, guaranteed profits, minimum wages, a right to relief, a right to the tools of labor, free credit, and so on, and so on. All these plans as a whole — with their common aim of legal plunder — constitute socialism.

Now, since under this definition socialism is a body of doctrine, what attack can be made against it other than a war of doctrine? If you find this socialistic doctrine to be false, absurd, and evil, then refute it. And the more false, the more absurd, and the more evil it is, the easier it will be to refute. Above all, if you wish to be strong, begin by rooting out every particle of socialism that may have crept into your legislation. This will be no light task.

...Socialists desire to practice legal plunder, not illegal plunder. Socialists, like all other monopolists, desire to make the law their own weapon. And when once the law is on the side of socialism, how can it be used against socialism? For when plunder is abetted by the law, it does not fear your courts, your gendarmes, and your prisons. Rather, it may call upon them for help."