Jacob. Let's say, hypothetically that you have a tapeworm in your intestines. Now, you want to go to the doctor to get a prescription for niclosamide to kill the tapeworm and get rid of it, so you can stop feeling nauseous and so on and so forth. On your way into the doctor a vegan stops you and says "You can't kill that tapeworm, it's a living thing, you have no right to get it out of your body. If you didn't want a tapeworm living inside you, you shouldn't have eaten contaminated meat." Does this vegan have any right to try and stop you making medical choices about your own body?
Now you'll say that this analogy isn't good, because the tapeworm doesn't have a soul, but the fetus does. Obviously my hypothetical vegan would disagree. That's just a personal belief you will say, but then, why is your personal belief here more important than his? Why do you get to impose this view on others through legal mechanisms while my hypothetical vegan does not? (For the record no real vegan would ever say that. Obviously they wouldn't object in the slightest to you getting rid of a tapeworm, and would then point out that if you didn't eat meat you'd never have ended up with one in the first place.)