THEY’re messing with the perfectly Created balance of nature

Where are the environmentalists demanding an environmental impact study?

Joshua trees aren't cutesy wootsy pandas, so they're taking the day off.
And the impact is tremendous, as Joshua trees have been in significant decline since the end of the Ice Age due to their main seed dispensers, giant ground sloths, having been wiped out by humans.

became extinct after the last Ice Age ended because of hunting by humans.

There's no historical basis for that. Any number of things could've wiped them out - hunted to extinction by other predators, disease, too much inbreeding which leads to infertility and/or genetic defects in animals.

Also if people can build solar farms then why not plant more Joshua Trees? Humans have transplanted plant life from one side of the planet to the other all the time.

Actually there is. Lots. All the way to beads made from their osteoderms in Brazil 27,000 years ago (Oh no! But Clovis!) and the last known species holding out in Cuba till 4500 years ago also becoming extirpated after the arrival of by humans.

What there isn't is any "historical basis" for is them existing for 35 million years then going extinct after humans entered the scene because the weather got warm and they caught a cold while getting eaten to oblivion by all the other predators they dealt with for 35 million years including the 8 million years in North America they dealt with new predators and diseases they hadn't dealt with prior to the Great American Interchange. Oh, and in eastern Siberia too, where their DNA had been found in the permafrost.

They're saving then environment by destroying it...

Follow the money

Because placing solar panels atop rooftops would mar the view of said rooftops.

No, they just mar the roof with hundreds of holes that eventually leak.

Not a complaint I've heard.

So obliterating delicate desert habitats is preferable to sufficient quantities of putty?

I think you misunderstood my comment. I was being sarcastic on the beautiful thing. These solar farms are a blight on the landscape.

.... using* sufficient quantities of putty

Oh, no, no perfect balance of nature. Quite the opposite.

Joshua trees have already been endangered, in steep decline since ground sloths - their major dispersers of seeds - became extinct after the last Ice Age ended because of hunting by humans.

Some rodents do spread their seeds, but that's locally, as opposed to a ground sloth traveling as much as 10 miles before depositing them along with a dollop of 'fertilizer.'
As a result Joshua tree territory has shrunken significantly for the last 10,000 years.

So this isn't like they can argue that they'll just grow elsewhere. This is a significant blow to the population, and irreversible. There was already another area decimated by a fire that had wiped a significant portion out.

If Joshua trees were cute cuddly polar bears or some crap like that this wouldn't be conceivable, let alone, permitted.