Shinra...

[Kefka_Almighty]

imagine ur mom was taken from u and u really wanted her back seph wanted to do anything to get his mom back what he did was wrong but he wanted his mothers warmth and wish and wanted to be a great son so what he did was wrong and evil but all he wanted was his mom

So merely having wanted his mom was justification for him to attempt to wipe out the human race AND the planet? While I can see how you came to the conclusion you did and Sephiroth's possible reasoning, I still say that his actions are unjustified and that his mere perceptions on things and people do NOT provided justification.

Also, yes, he wanted his mother's warmth perhaps to a degree, but even then the whole thing took on a new form as he basically really just wanted to justify destroying Shinra and the planet in a fit of rage to "avenge" his mom, or who he perceived was his mother, as well as spouting a bunch of racial superiority nonsense.

And, if we want to talk about his mother.......

(SPOILER)Jenova was NOT his mother; if I remember correctly, his real mother, Lucrecia, was infused with some of Jenova's DNA to see how the offspring of such a person would turn out, or Jenova DNA was added to him later on (it's been so long since I played the game that I can't fully remember). It's odd that the books he looked through seemingly never mentioned that, and to a degree I believe he really ignored it if they did; he had probably already come to view himself as a member of a superior race, and saying he was avenging his mother was merely a form of justification he could use to help ease his mind, if even that.