Here in the United States of America, since its inception, there has been a strong culture of self-reliance, of "work hard and be rewarded" and "I'll make my own way, thank you very much." This is manifest in how taxes have been applied to the citizenry. Until recent years (in the last 40 or so), taxes have generally been attributed to the direct benefit people derive from them.
For example, everyone benefits from a national defense, so everyone should have to pay for it. Some benefited more than others, having more property or means that are protected, and it seems fair they should pay more.
There is a usage tax on gasoline that makes since, provided the tax goes towards transportation infrastructure maintenance and improvement.
There was even a law passed recently that greatly increased the tax on cartons of cigarettes. The claim lawmakers made at the time was that the money received from this tax would be set aside for two purposes: 1) Help cover the increasing costs of healthcare cigarette users would require later in their lives, and 2) Cover the expenses of an anti-smoking campaign. Whether or not lawmakers have lived up their claims is debatable.
But the point is, it is generally understood that the revenue generated from taxing a citizenry should result in an immediate and direct benefit to the citizenry.
Taxing for the purpose of redistribution of wealth has always happened in the the United States. Historically, its impact generally only visible as a tax on the inheritance of an individual. Remember, we wanted, as a culture, to increase or continue feelings of self-reliance, "work hard and be rewarded for it," etc. So it makes since, from that standpoint to strongly limit how much money children inherit from the labors of their parents, since the more they inherit, the less inclined they are to work hard and be independently successful.
So, without any mitigating circumstances, it seems reasonable to me that a heavy estate tax should be acceptable. Should the government take it all? Certainly not. Should they take most of it? I don't want to get into details of how much the government should tax an estate. But remember, in a self-reliant culture, no one should feel entitled to money they did not earn themselves, regardless of their affiliation to the estate in question.
However, there has been a shift over the last 50 years or so, and a strong shift in recent years, to tax individuals in an attempt to redistribute their wealth before they die. Everyone should have a problem with this. If one works hard, one should enjoy the fruits of their labors. Others should not feel entitled to fruits for which they did not labor. To redistribute wealth prior to death removes the desire for excellence, self improvement, and hard work.
To forcibly take from the one living person and give to another living persion without the original receiving any benefit is theft, plain and simple. To take from an estate is not. They no longer live, no one should feel entitled to their estate. Taxing the estate encourages children to follow in the footsteps of successful parents by also working hard, exercising self-determination, and developing self-reliance. That estate money can then be provided, to those who seek to better themselves but are truly so far from resources at their disposal that they have no other choice but to turn to the government for assistance.