In response to the New York Times article Fate of Estate Tax Imperils Obama’s Ambitions:
1) "Studies show that the tax hits merely a sliver of wealthy American families." - This is really irrelevant in a discussion whether the tax is just and effective. If it hit only one family, would it be just?
2) "...simply a capital gains tax on investments that never previously changed hands." - Capital gain taxes are not 45%. Further, this is offered as a rebuttal to the "double taxation" argument, however, there is nothing in the estate tax to ensure that it is applied to previously untaxed income. If all the estate were created through ordinary income (and therefore taxed), it would still be subject to the estate tax. (Don't say it isn't possible; Lawrence Summers almost did in a single year.)
3) "They see it as a legitimate effort to require some of the nation’s most affluent families to share some of the rewards they have reaped." - On what grounds is this legitimate? Why is taking private property from one family and giving it to another legitimate just because one died?
4) Finally, the structure of creating a tax that by design hits only a minority but benefits everyone else is a form of taxation without representation; mathematically, it is impossible for the taxed to win a vote against this.
If taxing people with assets > $7 million is so good for society, be honest and tax people with any assets and redistribute to those with fewer assets; there are always people with $0 assets, and therefore in worse condition.