The particular map is about USA only, but in any case I can imagine many other places where agriculture and population would only benefit from such amounts of warming.

It's not so likely that USA+Canada+EU+Russia will make huge investments to fight a process that won't hurt them but will hurt, say, Africa and southeast Asia. If you want to convince people to take action, then it's important to focus not on global damage but on local effects, since those are far more important to both decision-makers and voters.

And this is not world map.