Idealism + political reality = compromise. That's politics.
Hear these words from an article in The New Yorker (September 5, 2011) by Melissa MacFarquhar, "HOW TO BE GOOD: An Oxford philosopher thinks he can distill all morality into a formula. Is he right?"
Suppose we who are living now decide to ignore global warming with the result that the lives of future people are much harder. It would seem that we have made things worse for these future people. But, in fact, as long as their lives are worth living this is not the case --because if we had acted differently, the world would have been different, and those particular people would never have existed . . . So although we have made life worse in the future, we have made life worse for no one [Philosopher Derek] Parfit calls this conundrum the Non-Identity Problem. (53)