I'll put it this way...
For example:
A man robs a gas station while beating the owner, and then steals all of the money.
He is, in the purest form, doing it for his own pleasure. He's doing it to get money, to add on his greed.
Compared to...
A man robs a gas station while beating the owner, and then steals all of the money because he isn't making enough to pay for his little sister's medical bill.
Are both these acts considers a crime? Yes. But was one shaped by his situation, and decided to act upon the crime with no greater intention than to improve his own greed? Clearly. Was one shaped by his situation, and decided to act upon the crime with a greater intention other than himself? Yes.
And to be clear, I'm not saying that point B was right in any way, shape, or form. I'm just pointing out there are differences between crimes made by no goal other than one's self, an then a crime created through your situation.
Point A being Orochimaru
Point B being Sasuke.
Orochimaru, like Sasuke, Nagato, and Madara. Had a choice whether to benefit mankind through his situation, but he chose to benefit himself. And that my friend is why he's a true form of evil in the series. This is why trying to prosecute those characters who were shaped by Shinobi World, like Orochimaru, but decided to change it for a greater purpose from their belief, is wrong. Especially since they were given a chance to repent their sins after they realized what they did is incorrect.
Edit; For the record I don't think Orochimaru helping in the War Arc gives him a free pass. He never felt truly sorry for what he did, even now what he did in Part 1 is still shroud in mystery. He's still a wild card in my opinion. I trust that guy as far as Sakura's character development went between Part 1 and Part 2.