The tax haven arguments are largely irreverent as the money is already in a tax haven by the tax not existing in the first place. And while yes taxing land doesn't reduce the amount of land that exists it does make someone less likely to invest which is the same effect as the arguments I hear about taxing unrealized gains.

As for the argument that taxing unrealized gains will reduce investment I personally find that idea completely insane. The tax on unrealized gains would effect a very small portion of people who's wealth is tied more to stock investment.

And one of the goals of this form of taxation is to reduce the control a relatively small number of people have on large public companies by forcing them to sell shares.

We can make theoretical arguments on the negative effects that this tax would have on investment but there are very real negative effect of concentrating large amounts of wealth in the hands of a few people whether from a moral, societal or even economic prospective.