Simply put, Rust is man's inhumanity to man turned into a video game. Playing reverts you back to all your primitive instincts, as you're plopped into the wilderness, naked and alone, and told to simply survive. At first, there's a satisfying peacefulness to the simple act of foraging for food, gathering rocks to hit against other rocks, and building a shelter out of whatever you can find. But then you remember this is a multiplayer game--and that moment of realization is probably going to be the exact moment that you are unceremoniously killed, stripped, and relieved of all your virtual possessions.
Like Day Z, Rust is a griefers' paradise, where the more sadistic among us can scrounge up a bit of in-game power, then torment, humiliate, and murder perfect strangers without a single consequence. Unlike Day Z, Rust doesn't even feel the need to factor in a zombie apocalypse or hordes of deadly NPCs to justify all this barbaric madness. Nope--it seems humans are just this horrible to one another by their very nature.