people do immoral things all of the time, but we don't generally legislate against them. it's just not a sufficient condition to ban or restrict something in a free society, where we reject the idea of the state as a moral arbiter and leave those decisions to individuals, instead.

and, we decide if something ought to have rights or not by legislating it. they don't have some kind of "natural" rights or something. from where do those rights come? there's no such thing as god, obviously - obviously. so, it's clearly not coming from some kind of supernatural decree, that's ridiculous.

we can consequently decide that, while it's immoral to kill the fetus, it doesn't deserve any legal protection under the law because it doesn't fit this set of arbitrary characteristics we've decided upon.

and, if we're honest, we have to accept that this is the actual legal regime, in truth.