This reminds me of the movie "Miracle on 34th Street".
Kris Kringle is deemed by the court to be, in fact, Santa Claus because the U.S. Post Office delivered mail addressed to Santa Claus to him. If a branch of the government recognizes him to be Santa Claus, then he must be Santa Claus.
But its even worse than that.
This argument is from silence without investigating that supposed silence.
The founding fathers definitely believed in the rights of the unborn.
They did not speak specifically to this because it perhaps seemed unconscionable that anyone would not know instinctively that the rights of the unborn were included.
James Wilson was one of only six men who signed both the Constitution and the Declaration of Independence.
He said “With consistency, beautiful and undeviating, human life from its commencement to its close, is protected by the common law. In the contemplation of law, life begins when the infant is first able to stir in the womb. By the law, life is protected not only from immediate destruction, but from every degree of actual violence, and in some cases, from every degree of danger.”
From this we learn that the founding fathers did, indeed, believe that the constitution applies to the unborn. What they did not know is that movement in the womb begins at least as early as when the baby's heart begins to pump blood at around 5 weeks.
For more info. on this please see:
http://www.lifeissues.net/writers/tay/tay_03foundingfather.html