The breaking up of inheritances may be the most common argument against estate tax laws but the instability of the laws may be the real issue.
The real reason estate taxes are unfair, according to The New York Times editorial "Why Taxing Fairly Means Not Taxing inheritances," is that politicians keep changing it. The argument was put forth by N. Gregory Mankiw.
While argument have been put forth in the past that the estate tax is unfair because it could possibly force heirs to sell off portions of their inheritances and that those who have accumulated wealth have a right to pass it on to their families, Mankiw argues it is the constant changes.
The idea is simply that because the estate tax exemption and rate is subject to change the amount of tax that has to be paid, if any, depends on the moment that a person dies. A person who passes away on one day can pay a lot more or less than a person who passed away the previously day if the law has recently changed.
The author believes that is not fair.
While this argument is unlikely to persuade people who support the estate tax, it might lead some politicians to consider how changing the tax can hurt people.
Reference: New York Times (Sept. 9, 2016) "Why Taxing Fairly Means Not Taxing inheritances."