What is ownership? You can only be said to 'own anything' to the extent that you are able to control it and use it for your own purposes. In a society of people, in order to do this it is necessary for other members of society to recognise you as the owner. This applies to any object - including one's own body. It is not an absolute rule that you are the owner of your own body. There are enough counter examples in history to show that this is not necessarily true. In what meaningful sense did slaves 'own themselves'?

Property rights are a framework determined by society - in modern societies property rights are created by the government. Taxes are simply part of that framework. It is therefore logically impossible for taxation to be theft because the government cannot break its own rules.