Okay, environmentalist wackos opposing urban sprawl at least makes sense. But opposing the spread of plants? What is this?
If they do not like wine plants, then they should buy that land.
Perhaps they can devote themselves to opposing kudzu!
While I am against 99.9% of anything Sierra Club is for, we have a friend who lived along the Gualala River on the Coast and visited often, it was/is a magnificently beautiful place with a lot of old growth trees; I would hate to see them go away and be replaced by vineyards instead. Of course, vineyards are probably better than pot growers who regularly use these forests to hide their crops.
I would imagine that the people buying the land know a lot more about what is "appropriate land to grow wine grapes on" than does the local Sierra Club activist.
It would, after all, be their business.
You misunderstand their fundamental goal. They think western Europeans are so evil, that this country must be cleansed of all traces of our existence. Pre-Columbian is a term appearing more and more often in environmentalist literature as code for "the way it was before that evil Christopher Columbus lead other western Europeans here". I know, I've been to some of their conferences, where they wax poetic about the pre-Columbian days, when everything was in the spot it evolved in... I could hardly keep from laughing!