My TA responded to my Glue Man example with the following counterexample: "Imagine that there is a very low probability that while playing touch football you could make a catch so amazing that it causes an epileptic man to have a seizure and drop his baby. I don't think it is therefore impermissible for you to play touch football, nor do I think that it is impermissible for an epileptic man to go to a park where people are playing touch football just because there is such a chance." I disagree that this counterexample demonstrates anything about the ethical status of tearing away from the Glue man, and I'll attempt to show why with a modification of the Glue Man scenario.
Let's say that Linda's pleasurable activity, instead of simply spinning around the darkened room with her arms outstretched, is firing a rifle in a random direction. Let's suppose that instead of the Glue Man being located in the room with Linda, there is instead a Glue-Man shaped board on one of the walls which can detect the impact of a bullet strike. In another room, the Glue Man himself is suspended above the floor in his unanimated state, and suspended from the ceiling above him is a grand piano. Suppose that the pressure sensitive board in the dark room is hooked up in such a way that if it is shot, the glue man will be released from his suspended position, and will land on the ground below. As before, the impact will jar the glue man to life, giving him full moral standing as a person, though he will be stuck to the floor because of the glue. A few seconds after this, the grand piano would be released from the ceiling, crushing the glue man to death.
It seems like this would be a case similar to the touch football example. The relevant question would be whether Linda would be permitted to fire her rifle randomly if she knew that there was a chance that she would hit the board, and this sequence of events would occur, resulting in the death of the glue man. To be honest, I'm not sure what to say about this. But I don't think that this is a good analogy to abortion, and I'll illustrate why by repairing the scenario to fit much more closely with abortion.
Let's say that just like before, Linda is in the dark room with her rifle, the board is set up somewhere along the wall, the glue man is suspended above the ground, and the piano is hanging over him. If Linda hits the board, the glue man will still drop, come to life, and be stuck to the floor (though the glue will eventually wear off). But this time, instead of the piano being released automatically after a few seconds, a lasso connected to the piano fires out of the wall and wraps around Linda's waist. As soon as the rope is secure, the mechanism that was originally holding the piano up releases, and Linda is left holding the piano up (we can suppose that the leverage in the system is such that Linda can support the weight of the piano, but it's an inconvenience to her). Linda could untie the lasso if she wanted to, but doing so would cause the piano to fall and crush the glue man.
It seems that this scenario is very different from the initial one, where the piano just dropped automatically. I agree that it seems somewhat worthwhile to ask whether Linda's shooting the rifle would be morally permissible in either case, and whether the moral status of that choice differs between the examples. My TA seems to be committed to the stance that in the first case, we would be able to construct the scenario in which the chances of Linda killing the glue man were small enough that she would be justified in shooting the rifle (perhaps the room is large enough that the chances of hitting any particular patch of wall are tiny). For my purposes, it won't be important to question whether this is true or not.
All that I want to suggest is that Linda's moral situation changes fundamentally from the first example to the second. We might think it permissible for Linda to fire the rifle in the first example, or we might think it impermissible. The answer seems to depend on how we deal with the concept of risk in our moral theory. But to be certain, if Linda kills the glue man, it will be the direct result of her choice to fire the rifle.
In the second example, on the other hand, the glue man's life is in no way put directly at risk by Linda's choice to fire the rifle. Rather, by firing the rifle, it seems like Linda enters something of a moral lottery. If she misses the pressure sensitive board, the glue man doesn't even come to life; Linda can go about her business without any real guilt. But if she hits the board, then the glue man gains moral standing, and Linda must make a choice: she can either deal with the inconvenience of being attached to the piano (until the glue wears off and the glue man can escape from underneath it), or she can untie the lasso, killing the glue man. It seems that whatever we want to say about the morality of Linda shooting the rifle (thereby "entering the lottery") in the first place, we would want to treat this outcome as morally distinct. And if Linda hits the board, it seems to me that we might very well say that she takes on the obligation to hold up the piano.
In the same way, I wouldn't want to say anything about whether or not it's moral to have sex if you don't want to get pregnant. But if we grant fetuses the same moral status as humans (which we agreed to do earlier), and if someone ends up pregnant in the same way that Linda ends up attached to the piano, then it seems like we might have reason for saying that abortion would be impermissible, just like it might seem impermissible for Linda to crush the glue man by untying the lasso after she had put herself and the glue man in their respective positions by shooting her rifle randomly. Does that make sense?