What if it's not sexuality per se, but rather the indulgence of human desire where there is the danger of it possessing the participant. I'm just thinking what the stoics might have to say on this, and they, too, would attach a stigma, but the stigma is more upon the idea of pleasure for its own sake. They would say let things indulge their needs, but nothing more. The way most treat it is in the way of it being something uncontrolled, hence the stoics would disagree with it according to their moral framework. What would you say to such a thing as that?
However, on another note, since, as you have said, it certainly is the responsability of both parties involved, why is the modern response then to absolve both of the responsibility (ie. have an abortion), rather than enforcing responsibility upon both? Personally I would much prefer the second option. Absolving people of responsibility is not a good way of running a society - if you will, there's my social commentary. This is one of the perils involved in abortions. Not to mention pregnancies in which abortions might be desirable are for the most part quite avoidable and, as you have said, it does take two. Except in instances such as rape, there is a willingness in both parties and, in some manner, in engaging in such activity they do enter into a sort of social contract in which their actions have reprocussions. The question of whether or not they want it after the fact is moot, in doing what they do - most especially unexusable since there are such methods as birth control - they have the responsibility for the outcome. To admit abortion, save for the most extreme circumstances, might be a disrespect of the woman.
Yes, you heard that right. It may be a disrespect. I believe it is Kant - though I only know this via my brother's ramblings - that speaks to the effect that criminials are punished because we respect them as humans. We act in accordance with the law to honour their choices. They have broken the law knowingly, hence to respect that decision, their human faculty of choice, we punish them as the law dictates. To remove that dehumanizes them. Likewise, becoming preganant is almost always done knowingly - that is, the knowledge that there is that risk. Barring more extreme cases (and it's better to argue the rules, rather than the exceptions), this is how it is. To remove the consequence of those actions is to disrespect the choice that was made, and in effect dehumanizes the person by removing the consequences to her decesion to have such sex. Such is one philosophical proposal which delves into the nature of choice itself.
So this is one of the problematic elements that arise. The issue is hardly clear-cut. This is a question that might be raised that is neither religious nor scientific, but rather philosophical. Indeed, it doesn't even deal with such issues as the nature of life, but merely with the issue of choice in and of itself. And it's something that I think is difficult to deal with. As I've said, these pregnancies are for the most part quite avoidable. If they have made that choice not to avoid them - through abstinence if that is the moral conviction of the person, or through birth control if that is the case - then to offer them an 'out' is to entirely disregard it.
I suppose I cannot get past the problem of the willingness involved. The choice is made already. If I went out and got myself into a dilemma which would require much work to get out of, and knowingly did so, would you consider it right that I could be excised from that responsibility? Perhaps it is an act of kindness, but even that act of kindness can have severe negitive reprocussions, as the sense of cause and effect can be tainted. Of course, an equal responsibility does lie upon both parties. These are social issues that are all connected to the issue of abortion that are not often addressed.
Nor, for that matter, is the validity of the statement that a woman should do as she wishes with her own body. Firstly assuming that one does have absolute supremacy over their own body (something that is taken true apriori, but is never actually proven to be the case... in the natural world this is certainly not the case, seeing as members of a species will sacrifice others for their own survival, in which the sanctity of the individual certainly does not exist), there is the problem of if the child is part of the woman, and if so, at what point does individual identity begin? (This is even putting aside the issue of what is 'life', and if life has sanctity... if it does not, there is nothing ethical wrong with killing... and if there is, what constitutes life?) Indeed, it is made all the more difficult by the fact that we have already assumed individual sanctity in the case of the woman... does this not extend then to an unborn child? And if it does not, then at what point does the growing creature become an individual human? At birth? What makes that the proper line, or are we arbitarially assigning it? Often it appears that while with the one hand we are applying an argument of personal right to the woman, we are ignoring that of the unborn child... and even if we assume that there is a difference... where does that difference occur? And if we cannot judge that difference, do we have a right to then arbitrarially choose?
Furthermore, there is the issue that, genetically, the unborn is not solely the mother's, but has elements of the father in it as well. As such, though it is in the mother, and connected to the mother, it is not entirely the mother's, save by a social distinction we have put on it in this current place and time. But if one wants to speak purely scientifically, there is a strong element of the father within it, and therefore to abort it is to damage something that is part of the father's body as well. Again, it may be inside the mother, but does that physical connection constitute a 'part'? If I lose my arm, is it no longer mine? If you were to cut off my arm, and take it, could you justly claim it because it is no longer connected to me? Therefore even if abortions are to be done, they should be in some part the decision of the father... right? Because though the woman has to undergo nine months of labour, what makes the time and work spent more valuable than the investment the man has put into it? Only if you can make a value judgement and quantify time and the like, and judge it greater and lesser and what not. And by what standards is that being judged to be so onus that it is worth an abortion?
You see, the arguments that are being made rely on a whole host of philosophical preconceptions that are only clear if they are assumed apriori and then has everthing else built upon it. But when one examines these foundations we run into some grave issues. Most importantly, we run into places where decisions and judgements are made rather arbitrarially, which makes any sort of scientific credence difficult to apply. Therefore the ethical nature of abortion really is not something easily solved, and goes beyond only the rights of the woman involved. To hold it only at that is dangerously simplistic at best. I don't think this issue has nearly yet been resolved, not religiously, not scientificially, and certainly not philosophically (probably the most important.)
One thing must be added. And that is the dilemma of views being tainted by preconception. What I mean by this is that Zelbess, for example, speaks that 'unless the traditional public view toward sex changes...', implying a very puritan and old-fashioned viewing of sex. However, when I look at the typical public view, I see it rather free and liberal. Now unless there is a difference between Canada and the US in this, it means that both she and I look at the same system yet, because of our natural bias, focus on different things to endorse our own world-view within that. That should serve as a warning to us that our views of the way things are are always filtered through some fashion of bias, no matter how objective we should hope to be.
I'm not really giving answers with this, because at this point - perhaps at all points - clear and decisive answers are horridly difficult to come by, and even more impossible to agree upon. But they are questions to be considered.