More easily demagogued, but difficult to tax. The only targets that are the least bit constitutional are wealth transfers or changes (eg estate, capital gains taxes). Taxing wealth ownership is difficult, and effectively unconstitutional, and therein lies the rub for progressivism, the folks that have the assets can shelter them from taxes by simply not doing anything...hence the "rich" is defined by income, and gets driven down onto the middle class.
I don't see how it's all that hard. As you note, it might be difficult to do a "wealth tax" but as you well know, most of the Old Rich aren't merely living off the diminishing principal of their fore bearers accumulated wealth. As a result, they tend to make capital gains. Capital gains taxes (if the democrats were actually after "the rich") would be their most demagogued issue.
It isn't. They want to raise income taxes. The SERIOUSLY rich don't make their money off of income. But what is the focus? Income taxes.
It belies either a complete inability to understand the nature of the wealthy in this country (I find this possibility extremely improbable), or an aim other than "soaking the rich". (This possibility includes the taking advantage of the public's misconception of what makes one "rich".)
I will state, once again, I don't think any taxes ought to be raised and I don't think the Old Rich deserve to be demogogued any more than those who actually produce goods or services and make income. I'm merely pointing out that "progressive's" stated goals and means don't match up. (My explanation for this is that they prefer to shelter the "old rich", just as there is a preference towards benefiting lawyers.)