@Jbcool Well, it's more complicated than that. The majority of loyalist legions see themselves as the protectors of humanity. They don't really judge humans as lesser beings, so much as they set themselves apart from them. Sure, there are some Astartes legions that could give two fucks less about humans, but that's more about the decisions of the chapter masters and the captains than the actual marines.
Remember, every space marine started life as a human. They've just ascended to the level of super-human. After that, they tend start thinking of humans the way Spider-man, or even Superman do. Separate, less powerful, and needing protection... but still living, sentient beings, worthy of both that protection, and of respect.
Especially for guardsmen. Practically any Marine recognizes that any given guard soldier is a hell of a lot braver than they are. Space Marines go into combat wrapped in power armor, wielding at minimum a chain sword and a literal hand-cannon, and with so many ogmentations that it takes absolutely ridiculous levels of firepower to actually kill them.
But Astra Militarum foot soldiers? They get a lasgun and flack armor, and they're expected to take on everything from hyper-evolved super aliens, to literal fucking daemons from hell. And those are just the ones that get training. Conscripts get issued a pamphlet on how to point their flashlights, and a complimentary wheel barrel to drag around their giant fucking testicles. And they're lucky if the Munitorum printed off enough pamphlets!