John Stuart Mill articulates the basic principle of modern libertarianism in his book On Liberty. He says:
The only end for which people are entitled, individually or collectively, to interfere with the liberty of action of any of their number is self-protection. The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others.
And on the face of it this looks like a great principle to base a libertarian system of ethics and public policy. And here is Ron Paul talking in very similar terms to the Mill quote, at least in the beginning:
But if you read further Mill extends the principle in a way that modern day libertarians fail to do. He says:
If anyone does something harmful to others, there is a prima facie case for punishing him—either by law or, where legal penalties are not safely applicable, by general disapproval. There are also many positive acts for the benefit of others that an individual may rightfully be compelled to perform: to give evidence in a court of justice, to do his fair share in the defence of his country, or any other joint work necessary to the interests of the society whose protection he enjoys; and to perform certain acts of individual beneficence. For example, a man may rightfully be held to account by society for not saving a fellow-creature’s life, or not protecting a defenceless person against ill-treatment, in situations where it was obviously his duty to do this. A person may cause harm to others not only by his actions but by his inaction, and either way he is justly accountable to them for the harm.
So, taxation, i.e. taking money from some people and giving to others, is not anti-libertarian. Taxation is perfectly consistent with a libertarian conception of government because as Mill rightly points out inaction can often be a form of terrible violence, and interfering to prevent violence is a legitimate government function. Bam!
Frankly it is hard to believe it is not totally intuitive, some theories on that forthcoming, but if you needed some justification there it is straight from the seminal work on libertarianism, J.S. Mill’s On Liberty.