Our society rewards successful entrepreneurs with wealth because, without their enterprise, we wouldn't have whatever it is we bought that made them rich. A low effective income tax rate on the creation of wealth is actually one of the cheapest ways to package that reward. Taxing success elicits less of it, and less success means less stuff for all of us. (Note that the list of low-payers doesn't include athletes and entertainers whose huge incomes don't come from capital gains.)

Lots of rich people own municipal bonds. Does anyone really think that lending to a municipality at tax-free rates isn't a form of tax?

The real mistake is that the estate tax is too low. Rich people should be allowed to accumulate wealth during their lives, because deploying wealth to create goods and services is the thing they do best. But when they die, their usefulness as capitalists dies with them, and dynastic wealth is an inefficient and dangerous allocation of resources.

(It's amazing what thoughts you can have when resentment isn't fogging your brain.)