Libertarian philosophy supports the pro-choice position

I accept my opponent's request to assume that life begins at the moment of conception. Also, I would like to acknowledge that the argument which I am about to posit is regarding an issue which is still hotly debated and intensely controversial within the United States (I admit I'm ignorant of the relative controversial status abroad). Therefore I will request that readers and voters (both of the pro-choice and pro-life persuasion) put away their biases and presuppositions and judge this debate purely on the merits of the arguments which my opponent and I put forth.===Incoherence of Positive Rights===The pro-life position contains within it a fatal flaw which makes it incompatible with libertarian ethics. This flaw stems from the fact that just as no post-birth person has the positive right to things such as clothing, shelter, medical care, etc. neither does a pre-birth person. In conceding that the foetus is alive at the moment of conception, it does follow that it possesses legitimate libertarian rights such as the right not to be aggressed upon and the right to retain a limited form of personal autonomy. However, nowhere in these negative rights does a positive right form. A positive right referring to the right to retain shelter within the mother's womb, nutrients from the mother, etc. Therefore the mother is under no positive obligation to keep the foetus alive.Now even if one were to concede that pre-birth humans are not necessarily entitled to positive rights via negative rights, one might still argue that positive rights aren't prima facie contradicting of negative rights. However this is improbable seeing as the only way positive rights may exist is through negation of negative rights. Consider clothing as a relatively simple example. In order to guarantee provision of clothing to person A, one must come into possession of the clothes from someone else, presumably the manufacturer. Let's call him person B. But since person B has a right not to have his property stolen (infringing on his property rights), fulfilling the alleged positive rights of person A comes at the expense of the negative rights of person B. And since negative rights (a la libertarian ethics) are already assumed there is therefore no reason to adopt positive rights into our framework.===Foetus as an Aggressor===This is where the argument gets more and more controversial. I advice readers and voters though to judge the argument purely on it's intellectual merit (i.e. on it's consistency with libertarian ethics). Under libertarian ethics, the mother has complete autonomy within the borders of her own body. The foetus, being within the confines of the woman's body against her will (presumably against her will being that the mother is seeking an abortion) is aggressing against the mother's right to self ownership and thus the mother is within her rights in stopping this aggression. Objections can come in a few forms and I will preemptively refute them here. One possible objection is that the foetus has no intention of harming the mother in any way (the foetus is not ven conscious) and I would not object that the foetus had no malice intentions. However, the question is whether (a) the mother's rights are being violated and (b) whether killing the foetus is the optimal method of stopping this aggression. On A, the answer is relatively straightforward. The mother has the right to control the inner confines of her body and not allowing her to remove an unwanted visitor is in clear violation of this right. On B, unfortunately removing the foetus immediately is the only way to stop the aggression being made.