NOTHING was justified, wtf. Did you remember how Rimuru murdered 100k soldiers, not for defense, but because he needed them to resurrect his friends?!
And it might suck from their perspective, but Rimuru and his friends ARE monsters after all. Humans lived for centuries if not thousands of years with the simple truth: monsters are evil. And before Rimuru named them all and thus gave them human-like intelligence, that was fair game for most of them. Sure, in this anime, goblins aren't murderers and rapists. But the direwolves were dangerous, orcs were, demons were, etc..
Sure, Rimuru can argue "you attacked us, we defend". But not only does that not justify the murder of the 100k soldiers nor the gruesome treatment of the humans in the waggon we saw this episode; it also makes him anything but a clean hero. And that's what this anime still pretends overall, that Rimuru is some cute, morally good hero. He's not. And if I were Rimuru, I'd question whether it's alright that everyone always kneels and bows their heads when he walks by. Not exactly healthy behavior unless you're a dictator who gets off on power.
Tbh as I'm typing this, I'm wondering how humans even survived this long, considering there's not a single human so far that could keep up with the demon lords we saw. Rimuru is one of them and it shows. To those who read the light novel or whatever the source is: Pls send me a PM and spoiler me with a yes or no: Does anyone ever oppose Rimuru and Rimuru is forced to realize that he's in the wrong? Thx