Rancho Palos Verdes is a small established hillside community with equestrian 1 - 5 acre lots. The absurdity of adding 650 homes to this area is astounding. Right next door is Hawthorne which has plenty of space for such housing. Activists like this person, lobbying a city they have no relation to, to enforce an overreaching state law, are part of what is making people and companies leave California.
OP said "established hillside community with equestrian 1 - 5 acre lots".
It is reasonably likely that people who lived there chose the location because they wanted to have horses, otherwise why buy there?
When dense apartments get built next door, soon enough the city prohibits horses because the thinking goes that horses don't belong in a dense population area.
I'm not familiar with the area OP mentions, but exact same thing happened around here. Some 30 years ago most houses had horses, then a lot of smaller building came around and they prohibited horses.
Doesn't impact me personally but I'm sad for the long time residents who specifically moved here to have horses. Not fair to them. Some have moved of course, but moving isn't always easy if you have job and kids in school in town.
If the neighbors of these lots care to maintain their vacancy, they ought to do so the more naturally legal way: by collectively buying and owning those lots.
Which is likely why they are doing it. The City of Huntington Beach had a similar problem: there was simply no room to build additional housing. They sued the state and lost. The law is overreaching, but it's the law.
30 minutes drive in no traffic, crossing half a dozen cities and the 405. There's reasons to inveigh against the YIMBYs (why are they celebrating densifying a coastal area that's actively falling into the pacific[1], nevermind it's inherent beauty) but let's not deny geography.
Also RPV doesn't have 1-5 acre lots, it just costs ~$4m for an house on a normal lot, rising to ~$20m as you get to the coast. You might be thin thinking of Rolling Hills, to the extent you're thinking of anything on the peninsula at all?