Honestly, i could swap some words and to say that SU is anti-right propaganda. This guy takes vague ideas and repurposes them under his agenda, because those are vague ideas, generic storytelling tropes.

More specifically, the gems rebelling against that authority that enforces a caste system, where people are fixed into a certain fate because of their birth conditions, that they are can't (and shouldn't try) be more, like the tired-old concept of racial superiority. Merely disagreeing with the regime, doesn't he think that an ultra-right organization wouln't try to prevent that? In fact, demonization of the arts and academics/sciences is a sign of fascist regimes.

Regardless, the creators of the show made clear multiple times that the message is about diversity, with multiple female characters that arent "traditional", both in personality and physical looks, the people's psyches (people, men included, getting emotional, seen in certain circles as a sign of weakness), LGBT+ people (as much as they can be without calling them as such, because the people at Cartoon Network wouldn't like it), challenging the norm. The part about hierarchy is more of an extension of the previous. That is the reason /pol/-types dislikes the show and tumblr-types love it.

I wouldn't say that Homeworld doesn't see any value in the gems. Remember when Peridot contacted Yellow? She had royally fucked up and yet Yellow was still willing to give Peri a ride back home, even willing to forgive her for her outburst after that. Or even Jasper, nothing more than an Earth-made soldier but she still sent a party out to find her.

Though, considering the latest episodes showing Yellow's disdain for Earth-gems, I do question why she has Jasper working for her. (Granted, it's more towards Rose Quartz gems, but there's a clear spite toward the kindergarteners.)

And I wouldn't say the Zoo is entirely a safe-space concept. Eden maybe, but nothing SJW related. It seems more like the Zoomans are the physical and real representation of what the Gems view humans as. Much like how Rose herself didn't take humans seriously until Greg opened her eyes, they were cute little things to play with. Or like how Holly saw them as noisy animals. That's why they're pampered and taken care of as if they were pets. All in all, Pink Diamonds treatment of humans seems very similar to how Rose saw them, which is probably intentional.