Is there some rationale for setting the LVT rate so that the land is worthless?

That seems unnecessary and counter-productive. If I were designing the system, I would want both the government and the landowner to share in the appreciation of the land. If a nice park is to be built next to some land in a city, interests are more aligned if both the city and the landowner share in the benefit.

Because land belongs to society at large. The entire idea that someone can own land is nonsensical. Private ownership exists to encourage people to create stuff but land can not be created. When land value increases it is not because of anything the landowner did, but because of what society did. The gains should go to society.

Its also more effective at removing speculation the higher it is. LVT is one of the few taxes with no deadweight loss, so even if it wasnt the most morally acceptable tax it still is the most economically beneficial one so we should try to collect as much as possible through it.

>When land value increases it is not because of anything the landowner did, but because of what society did. The gains should go to society.

Nicely landscaping your home can increase the surrounding home values, especially when other neighbors do it also. Conversely if neighbors have junker cars and trash on their property or if you're in a city surrounded by abandoned buildings, land value decreases.