That's not how legislatures work. It's like saying, 'take Senator Jones off the HHS committee because they are anti-vaccine' - the people in Senator Jones' state are entitled to representation with complete disregard for whether others like their Senator. Legislatures work with power as it is, not as how we want it to be.
> for what little the UN does
People on the right repeat it, but repetition doesn't make it fact. What do you know, specifically, about what the UN does (about human rights, if that's what you mean). The foundations for international law, which is powerful and effective though imperfect - like domestic law, but lacking the same enforcement mechanisms.
> [China and Mexico]
If everyone stopped doing all business with anyone in a country that does bad things, there would be no business or trade. Trade enriches the US, and has lifted billions out of poverty - including in China and Mexico.
Putting them back into poverty is just reckless. You need to come up with a better solution to your leaky roof than burning down the house.