A tax on property isn't theft when property is theft. The Earth belongs to everyone. Hoarding a part of it exclusively for yourself is theft, because you didn't produce the Earth. You are only entitled to the product of your own labor, not to natural wealth. Private property in land is theft. Land value tax is not theft, but merely a way of making private property in land acceptable. I.e. Land value tax makes private property not theft. If you oppose land value tax because it's "theft," then you logically also need to oppose private property in land altogether, because that's also theft.
Also, beyond private property entailing theft now, the institution was historically rooted in theft in other ways too:
https://steemit.com/anarchism/@ekklesiagora/property-as-theft-the-libertarian-socialist-critique-of-property-part-2
RE: Beyond the Capitalism/Socialism Dichotomy