No the reasoning might be that if you're involved in politics, you're involved in national politics, as you don't have the possibility of trying to take over the world government, and if you're involved in national politics from a "left-wing" point of view, because you care about people? you actually have to limit that to caring about the people of this country, irrespective of their race, rather than caring generally about the people of every country. And perhaps you realised that a compassion so generalised that it doesn't distinguish between people from this country and people from others, is also one that doesn't have much appeal to your natural political constituency, and so its only virtue is really that it's a morally impeccable viewpoint, but at the price of having any political effectiveness.