2) If every democracy uses uses nuclear power everyone else will want it. And if you have a nuclear plant you have most of the really hard bits of a nuclear weapons program. Untrustworthy countries who probably shouldn't have the temptation of city-vaporizing weapons will want them. And it's kinda hard to convince an Iranian who thinks his country is perfectly trustworthy (to him it's those nasty Israelis you have to worry about) that everyone's life would be so much easier if his country didn't have the physical capability to finish the Holocaust. It's even harder to convince the Israelis, who (probably) currently have nuclear weapons, that everyone's lives would be so much simpler if they just switched to solar.
In other words if the choices are one or two more degrees of global warming, or letting every country in the world develop nuclear power, we're probably better off living with the warming.
This is one of the shittiest arguments ever. Out of all countries with nuclear capability, US happens to be the only one who has actually used nuclear weapons against another country. Additionally, the US has started several new wars in the past decade alone. So if we go along with your "trustworthy" line of reasoning, the US should be #1 on the list of countries to be denied any access to nuclear technology.