Darkin do not have the capacity for love, but instead, their most positive emotion is respect. Being a culture heavily steeped in war, they admire strength in others and will defend it as much as they can. A Darkin shows affinity by training the person in combat and helping them sharpen their skills. To see them succeed is a great satisfaction.
And so when Aatrox inspires soldiers to fight, he does it out of respect for humanity. He wants them to chase their goals. He wants them to flourish. By Darkin standards, Aatrox is the sappiest, most hopeless romantic entity of war there is. No one is quite so invested in humanity as he.
Of course, by human standards, he’s seen as an instigator of needless violence, but hey, you know— can’t win ‘em all.