This can't be a serious objection. Why should people work hard to get rich if they can only pass enough on to their kids to ensure the kids never lack for the slightest material need (unless they're idiots)? Well, there's the cars, houses, fancy foods and drinks, vacations, multiple homes, glory of self-funded political campaigns, better health care, potentially the joy of charity and seeing your money do good in the world, the best education possible for their kids. You might not believe this, but there are hardworking rich people who don't have kids at all! Yet for some reason they get rich anyway.
The parents are now dead. The only thing the kids did to "earn" their parents' money was get born. They're still keeping whatever the exemption is, which is a very large amount of money, as well as the immeasurable advantages of quality educations, networking with other power elites, and hopefully their parents have instilled the values of hard work that got them there in the first place.
But imagine if the estate tax above, say, $5million, WAS 100%. What are people going to do? Aside from tax avoidance, my guess is they'll donate to charities of their choice rather than give it to the tax man, which benefits everyone. Possibly they'll spend more during their lifetimes, circulating money back into the economy and adding some small amount of reality to trickle-down theories. Maybe they'll create jobs and pay their employees well, since they can't take it with them. Or, maybe they'll just let the government spend it, where it can go to any number of good programs that help millions. Look at the examples of the robber barons of our own history - they raised huge amounts of money in their lives, then spent it on the Rockefeller Foundation, University of Chicago, libraries across the country, and other programs that have done enormous good for the entire world.
Yes, I want to be able to set my kids off on the right path, and that's why we need an exemption. We don't need more Paris Hiltons in the world.