It's the principle of the thing. If ownership exists over anything, it's your own body.

You should get to decide what happens to it, even though you have no ability to enforce your will into the future.

Vultures stealing your property will always try to justify it in the name of the collective good. i.e. If you can't convince someone to give it to you, just take it.

There's also the question of who would get to take it, and why them specifically and not someone else who might need it?