"In the US, property tax is based on current value of property (cost plus or minus unrealized gains). So taxing unrealized gains in the US is not a new idea."

I just don't view it as being the same. Property taxes generally go towards funding local community issues- schools, roads, local initiatives etc. It is not so much a tax on unrealised gains as it is a fee for general upkeep of the community.

Taxing market equities (which fluctuate way more than housing prices) is just a general income tax. There's a reason why we don't tax unrealised gains- because they can change wildly from one year to the next. Again, I'm all for closing loopholes, raising tax rates on realised income and trying to come up with a more equitable solution where the uber rich are paying their fair share but this is not the way to do it. Part of the collateral damage is that the small investor gets hurt particularly if there is no exemptions. I would think that there would be exemptions but where does it start? $1M? $5M? $10M?