Defend equal rights for all (including the unborn), with special privileges for none
The fundamental reason that all have equal rights is that they all are endowed with those rights by the same Creator. The time of the endowment is the moment of creation (procreation if you will), and the duration is until revoked by the Creator.* We have it on good authority that the only time that the right to life is revoked is when certain Divine Standards are ignored, and that it is not an option at that point. The unborn have had no opportunity to commit an infraction! The right to life is forfeited by the taking of innocent life either in whole, as in murder, or in part, by some other act of violence against one or against many, as in rape, treason, bearing of false witness, etc. (In case you wondered, pro life Libertarians are not unusual. You might want to visit the website of Libertarians for Life. They approach the subject rationally, rather than religiously. Congressman Ron Paul of Texas, a former Libertarian Party candidate for President makes a strong argument for the pro life position.)
The Creator of the universe gave equal rights to all, because they all equally share in His image and likeness by common genetic parentage. There is therefore no basis for humanity to grant special privileges to any class of people under force of law if that class is not the direct result of an act of God. There is a difference between male and female that is the result of creation and there is a difference between youth and old age and all the intervening stages of life that is the result of creation. You may be able to think of other differences that you might attribute to Divine Design. I'm open to your comments. Write me!
A good case can be made that the difference in how people think and how they choose to act is a different matter, as is the results of accidents no matter what the source or the result. They should not be accorded special privileges under law based on those circumstances. They should, however, be free to think and be as they wish if they are not interfering with the exercise of someone else's freedom. In this life they have the right to be wrong; they are accountable to God, not their fellow man in any matter that does not impact another human being's rights. I should be at liberty to show partiality in a case of genuine hardship by giving of my time, effort, and resources to help the one(s) I wish without being forced to do the same for all other people whether in that condition or not.