Sokka isn't privy to Katara's internal battle, but he also hasn't seen Zuko and the extent of the horror that the poison has done to him. He doesn't know Katara's difficulty over her inability to help Zuko and her being forced to resort to the last method to help him that she had, namely forcing him to not kill himself. But he will stand by every word he said because, even if Katara was feeling scared and defeated and forced into a corner, it was being able to act upon those higher instincts in spite of fear and terror that defined a warrior.

After all, she did have the Mark of the Brave. That symbol was well deserved.

"Then we'll just have to keep looking. I don't know what this poison or this Spooky Spooky Witch Person can do, but there's got to be something. I really need to catch up on that and see what's out there."

He gently pulls Katara closer. He can feel her sobs and her jerky breathing. He knows she's in a dark place... and hurt both physically and mentally. He wraps his other arm around her front, letting her lean upon him and hopefully pulling some of her negativity into him.

After all, he was the pessimist around here, dang it, and the rightful relationship between the siblings had to be maintained.