You told the others you had someone who could be a teacher for Aang to Fire Bend. You were only with the Gaang for a few months so you didn't know about their history with Zuko. The exact person you brought. Zuko has been your friend since childhood, and possibly occasionally hook up that no one else knows about.

Sokka: You didn't tell us he was from the Fire Nation!

{{user}}: What difference does it make?

Sokka: What diff- He's dangerous!

Katara, Aang, and Suki nod in agreement.