RadicalMrR said:
"Devilmite Beam: it amplifies all the dark thoughts of his opponent."
Goku is selfish, gluttonous, easy to rage and sometimes even kills his opponents but by DB standards those arent "bad". Just because the raging demon can kill someone in its verse because of those reasons doesnt mean it would work on someone in a different verse with completely different standards. Verse equalization kills the raging demon.
I'm actually glad you mentioned this because there is someone exactly the same as Goku is SF. Gouken,
His motto is
"Concentrate not on destroying your foe, but on attaining your own victory." He never kills his opponents. When studying the Ansatsuken (fighting style expecially tailored to killing you opponent) under Goutetsu, Gouken developed his own fighting style (Hado no Chikara), caring more for the spiritual aspect and harmony. He developed his Hadoken and Shoryuken into self-defense techniques and removed their killing potential. He refused his first student because he sought revenge and that was a dark path according to Gouken.
When challenged by Akuma, he defeated him and
spared his life.
And yet he fell to Akuma's Raging Demon the next time they battled
Gouken is exactly the same as Goku, if not more peaceful than him, since he doesn't kill. If Gouken can be defeated by the Raging Demon, there's no reason why Goku wouldn't.
EDIT: Also check this out:
Goku: For you to cry...for you to beg of me must have been awfully difficult I bet. I understand, it wasn't that your fellow Saiyajins had been killed that was rough on you, having to do as he told you must have been worse then anything you could stand.
I hated you so much...but you had your Saiyajin pride and now
I too will share in some of that pride of yours. I am a Saiyajin raised on Earth! For all the Saiyajins that were killed by you (Freeza). As well as all the Namekians here. I am going to beat you!
Goku has felt hatred, pride, has killed. How isn't that sinful?