karkatpantstoss said: But it was the woman’s choice to have sex, assumedly, so why would it be the fetus forcing her to carry it and not her forcing the fetus to exist?

Not disagreeing with that.  Personally I think a woman has to be quite irresponsible to have an unwanted pregnancy with modern technology and family planning. But with that said that doesn’t reverse the rights of women. 

Like I said to Megan, even if I invite you and chose to have you over my house I still have the right to evict you if I no longer want you there and you refuse to leave on your own.  So it was my choice to invite you over but that doesn’t reverse my rights as a property owner. 

The fetus doesn’t have the capability to force someone to carry it against their will.  Only people who are willing to use force and against against a woman have capability to force a woman to carry it to term. 

Using force and aggression against someone to do something against their will is a violation of the non-aggression principle.