Biden didn't defend the concentration camps. He clearly spoke of them as human rights abuses. When Biden said, "culturally, there are different norms that each country and their leaders are expected to follow" he wasn't referring to the camps. He was referring to the expectation that, yes he will speak out against human right abuses in China, to the Chinese President, regardless of the norms in China about what the leader says. That's what the President of the United States does - reflect the values of the United States.