I’m a big fan of the G1 Cartoon (specifically, Five Faces of Darkness) origins of the Autobots and the Decepticons, that is:
Both of them were created by the Quintessons. The Autobots were a the civilian product line, basically robots servants. The Decepticons were war robots.
The reason I like this so much – and of course this was never explored explicitly in G1 – is that it explains and problematizes the tendency for Autobots to value other species’ lives and interests over their own.
They were built to serve other species, so of course they protect human lives above their own. Whether or not this is a more ‘moral’ choice objectively, it’s a bias wired deep inside of them. So you get things like Skyfire, seeing humans for the first time and coming to a screeching halt – he can’t hurt them even if Starscream tells him they’re the enemy.
Meanwhile, Decepticons were built to fight other species (and probably different factions of Quintessons as well) so their relative xenophobia – and tendency to fight for what they want rather than negotiate or make friends – makes perfect sense.
Cybertronian Database 