> By extension any woman who suffers a miscarriage is a murderer
With all respect, this is not "extension", but rather "gross distortion".
> It prevents most of the money in circulation from accumulating in the hands of a very small number of individuals.
What if such accumulation was just? Would it still be wrong? If yes, then why? If no, then what's the problem? Shouldn't we worry about making game rules fair, rather than making sure outcomes are "equalized"?
Maybe you want to live in a society not unlike the Gilded Age where billionaire robber barons controlled everything, where those who weren't part of this small elite group could barely get by.
This is how un-checked wealth accumulates. Remember, it is very easy to make money if you have lots of money to start with and can weather almost any risk no matter how severe. When the smaller players bust out, the wreckage of their companies and lives is bought for pennies on the dollar.
Would you want to live in a world where the Paris Hiltons could coast into billions of wealth without having to do a single hard day's work in their life? Where they'd have enough money to fund a hundred generations of that?
Society advances when there's an incentive to working hard. Making money is one such incentive. When you can make money without working hard, it starts to break down. The inheritance tax is a way of keeping an element of hard work in the equation.
Ah, but you've said 'robber barons'. This is exactly the thing - robber barons. Being a robber - a bandit or baron, no difference - is a bad thing. It's where the problem is. "Robber barons" use money and violence - rather, they use money to "rent" violence from its providers - to create barriers to entry - as you've said, "could barely get by". This is not even close to what libertarian stand for.
As for it being easy to make money if you start with a lot - why, this totally depends on the rules of the game in question! And if the game is fair and open, then it will be equally easy for the rich starter to squander all their wealth - since they don't actually produce wealth, but only consume what was inherited.
Libertarians are, first and foremost, about a free and honest game.