That is the problem with abortion arguments. They are simply not morally consistent. The "my body my choice" statement has nothing to do with the debate. Clearly we do not use dependency as threshold for killing someone in any other situation. It is unfortunate that pro-lifers tend to use religious arguments to justify their position, which completely devalues it in any secular discourse.
There is no consistent definition for "what is a person", and no convincing argument of why a fetus is fair game. I am about as big an atheist as it gets, but I do not think abortion is justified in most situations (it is in some though). I've had very serious discussions on the subject with intelligent and educated people, and it always leads to questions about why is it wrong to kill babies, or the elderly, and so on and so forth.
