That the Left (or what passes for the Left) is against this is the craziest thing.
It comes down to the issue of ability to pay. And because they don't actually have the data presented to them to show that a site/land value only tax IS actually progressive they can't see it as a viable option.
Do you think that well meaning guy who wants to protect the working class and soak the rich would have a different tune if he saw the data that shows that land value is even more maldistributed than income? (This is why I did a study: "Who's owns Baltimore?" to find out. 58% of the land value is owned by the top 10% of the land owners (all corporations), while the botton 10% of land owners own less than 1% of the land value. (So that bottom 10% of land owners does NOT include the 45% of households don't own any land at all.)
The poor widow/pensioner raises it's head, but give me the names and addresses and let's really see.
This is why apart from any theoretical reasons - a per capita exemption or a household exemption for primary actual residence makes LVT more sellable to the left because it ensures that, even if there were any true doubt, an LVT can be implemented in a way that is IN FACT progressive.
I am presuming that the Stamp tax they were talking about is what we'd call in the US the title transfer tax.
And it was not particularly clear would the proposed Site Value tax fall on all land or just residential land, because it really has to fall on all land value.
You've got to have the data set to show the progressivity. You can't just say it, you have to show it. ("Prove it, before you promote it")