I know this thread is two months old but I had to comment. If you base your entire philosophy on a scientific theory that has a weak foundation, then when that foundation crumbles the philosophy goes with it.
Tabula Rasa is a pretty outdated and unscientific concept, if you read Steven Pinker's The Blank Slate he does a pretty good job of dismantling the nominal subject, and goes on to explain why we don't need the blank slate to preserve our virtues anyway (indeed he demonstrates why it would be worse).
If Objectivism relies utterly on tabula rasa than all the worse for Objectivism.
Melchior got a reaction from chuff in Tabula Rasa