Is poison use evil?

[Eldariel]

Which does nothing to explain why that requirement is actually there or mitigate the raw stupidity of it, even if that's what it actually was.

Assassin-class was originally used for a very specific organization of assassins hence the prerequisite. It's just presented in a general manner in DMG and thus the prerequisites seem kinda weird.

And no, obviously using poison is not evil. Poison is a tool, what matters is how it's used. Using a poison/sword/fireball to kill a Red Dragon? Fair. Using them to kill an innocent human child. Quite evil. Absolutely no difference between poison and other implements of death. Even the "fairness"-argument is kinda...casting Invisibility is no less underhanded than poisoning food. So, yeah.