Candidates only talking about one means that they don't mind about human rights, that they are only doing these for , economical reasons, someone wants to wage a economical war with China that will cost USA lots of money, but some companies will get huge amounts of money and power, so first you declare them the evilest country in the world and then continue.
They did it with Afghanistan , later with Iraq.
OTOH the are silent about other places like SA or many other dictatorships in the world. Hypocrisy and blatant lies about human rights. And yes, the Chinese government is really fucked up. No one can deny that.