Goku: "Why would I want to fight them? They wouldn't be a challenge at all! Now excuse me, I have to endanger the entire universe yet again so that I can get my battle fix."

That's because there are no racists in the Dragon World, everyone lives in harmony. Even the furries. Dragon World is literally so tolerant they let an anthropomorphic dog man named King Furry be president of the world. There are a few space racists but he's killed the only prominent one of those twice.