Here's a shock for you: Whether abortion is murder or not is not, in my opinion, the question. How, you ask, can that be?
I believe that abortion is immoral and wrong and could be included within the prohibitions contained in statutes that define and provide for the punishment of murder, even in the ways mentioned in the amusing link that you included.
However, there are some things that are immoral and wrong that cannot effectively be criminalized, or if criminalized cannot effectively be enforced and punished, without intrusion by the government into the most intimate and private affairs of its citizens in ways that the citizens at some point find intolerable.
In cases where the citizens do find investigation, enforcement, and punishment intolerably intrusive on their most personal and private affairs, the citizens acting through their elected representatives are entitled under our Constitution to decriminalize previously criminalized immoral and wrong acts by amending or repealing the law if they so choose, or, if they act in time, to prevent its enactment in the first place.
For this to happen, it isn't necessary that the governmental intrusions in question themselves be unconstitutional; it is necessary only that citizens in sufficient numbers to compel the amendment or repeal of the obnoxious law find its enforcement to be intolerably intrusive.
Legislatures are never required to grant to law enforcement agencies all power that might constitutionally be granted to them. And law enforcement agencies are not authorized to exercise all powers that might constitutionally have been given to them if the people have chosen in specified situations to rein them in by law short of granting them all the powers that they might have been given under the constitution but that in particular situations were withheld from them or denied to them by law.
As an illustration of this principle, state and Federal reactions to the decision of the U.S. Supreme Court in the Kelo case, upholding the constitutionality of the use of eminent domain powers by units of local government to take property from its owners involuntarily for transfer to other private owners in order to enhance the tax base rather than taking it for governmental use as a highway or a courthouse, for example, are now proceeding in Congress and in various state legislatures and will undoubtedly result in powers that the U.S. Supreme Court is willing to allow public bodies to exercise under the constitution being taken away from those public bodies by law.
This is the way our system is supposed to work.
There are actually three questions embedded in your one question:
1. Can abortion constitutionally be included in the statutory definition of murder?
2. If it can be constitutionally included in the statutory definition of murder, must it be?
3. Even if it can be constitutionally included in the statutory definition of murder, are the people willing to permit the intrusions into their privacy that would be needed in order to enforce a statutory definition of murder that included abortion; and, if the people would in fact find those intrusions to be intolerable, can the people, assuming the existence of sufficient political strength, refuse to permit the enactment of a statute that includes abortion as murder, or, if such a statute has been previously enacted, compel the amendment or repeal of the provision or provisions they find intolerable?
My responses to those three questions would be "yes," "no," and "yes."