Why people think the US is so great in human rights?

Whenever there is an issue about China, it always managed to turn into a discussion about human rights. I always wonder why people felt that US is anymore better than China when it comes to human rights. The US has a history of supporting oppressive regimes. The current current crisis in Egypt is just one example. The US has been sending aids to support the regime in Egypt, but at the same time, this government is oppressing it 's people. The US is doing this all in the name of "American interest". I wonder why people think the US is so great in human rights? Where is this moral authority coming from?