Because Vegeta represented the pride of the Saiyans. Goku said it himself that he wanted to share some of Vegeta's Saiyan pride before claiming he's fighting for the Saiyans. He also said that he hated Vegeta, just like he hated the Saiyans.Doctor. wrote:Nobody is denying that Goku thought the Saiyans were better off dead. But just like he was avenging the Namekians, and Vegeta, he also put it upon himself to avenge the Saiyans, he says it himself. Why he did that is up to anyone's guess.TheUltimateVegito wrote:Either way, I'm sure he meant that the Saiyans were just as bad as Freeza, so he believed they were better off dead. Goku was definitely himself, despite being angry. I mean, he did want to spare Freeza after all. And I don't recall him acting differently during their fight, like Gohan did when he fought Cell.
And Goku did lose a part of himself during the fight, that's the main point of the SS transformation. Kaio puts it very clearly that Goku is no longer himself but has turned into the Super Saiyan, "a warrior whose heart has been awakened by rage". Goku only regains his personality back when he calms himself down later on in the fight.
And I'm sure he meant what he said still. It's like saying Goku didn't meant anything else he said simply because he's angry.





