It also only applies to a fetus created as the result of rape. A fetus created by consensual sex is like if you walked into the hospital, sat down in the room, and plugged the needle into your arm yourself.
At the risk of stretching the metaphor to its breaking point, this is you choosing to go out and get drunk while aware that members of an unethical music lovers' organization are skulking about looking for victims to graft sick violinists onto. Sure, they no longer need to actively drug you because you willingly did that yourself, but that doesn't imply your consent to what happens next.
It's as much consent to pregnancy as dropping a cinderblock on your foot is consent to a broken toe or eating ten cheeseburgers a day is consent to getting fat.
People around the world routinely engage in frequent sexual intercourse without becoming pregnant. If you show me even a fraction of that same number of people who have demonstrated an ability to consume ten cheeseburgers a day for a prolonged period without gaining weight, maybe you'd have a point. Otherwise, this is just a blatant false equivalence.
Yes, and people routinely take methamphetamine without having a heart attack and shoot themselves without dying. That doesn't obviate the fact that pregnancy is the direct result of coitus. Claiming you did not consent to the function for which a body part evolved when you used that body part is like saying you didn't consent to sweating when you went for a summer jog. Sure, you may certainly take measures to prevent an undesired outcome but the physical results of your choices can only be tragedy, not injustice.
Social constructs don't apply to biology.
From my perspective, even if we assume the person plugged the needle into the arm, it's absolutely not my place to mandate that you must now keep the needle attached until the violinist can live independently again.
You may feel horrible about disconnecting that needle. We may even agree that it's a pretty awful thing to do to the violinist. In fact, we may even agree that you should be responsible for at least attempting to find alternative options for the violinist. But I certainly would never imagine creating a society in which we would prevent you from doing it. It is your body, and you should absolutely retain the right to revoke consent for the violinist to live off of it.