As others have said: Doubletap.
One thing to mention is that probably a decent majority of „Humans“ in the Imperium live in like one of two conditions:
Abject slavery. They do backbreaking labour hauling munitions on starships, toiling in the fields on agri worlds, or just otherwise being downtrodden and beaten back into place when they stop to breathe.
Servitor-ized. Cybernetic Lobotomy. Used to carry out menial tasks or as biological stand-ins for advanced computational systems.
The backbone of the Imperial industry is slavery. Millions upon billions of people reduced to gears getting ground down in an unfathomably large machine. And that machine is a bolter aimed at literally anything that conceivably opposes the Imperium.
I‘m really debating the ethics of as to whether or not pulling that trigger is a mercy or not for a lot of Humans. There are countless generations of Humans aboard ships or on industrial worlds who spend their entire lives never seeing the sky, breathe fresh air, or drink water that hasn‘t come out of a filter. they live, breed, and die carrying out tasks whose greater purpose they have no real concept of. Those who dare to step out of line become an example for others.
Have you ever looked into Imperial ships? Even the smallest classes have crews numbering in the tens of thousands. And those aren‘t all crew and officers. They‘re almost certainly 90% slaves. Every. Single. Ship. Tens of thousands in a battlegroup. Millions in a fleet. And that‘s not even considering the billions who must work on the uncounted millions of freighters, transports, liners, and other civilian craft who form the lifeblood of the interstellar trade network.
The comparatively sparsely populated civilized worlds or paradise worlds where people might live marginally freer lives cannot possibly outweigh the untold billions who toil away in the Hives and factories.
And the people at the top have no concept of those at the bottom. They are just numbers. Just Mush. If billions of dregs must die so that the Xenos are extinguished? Better the Dregs than I.