Realism v. Idealism

When thinking of politics and the root of the words realism and idealism, which sounds more usable in relation to international and domestic policy.  Sure, ideally we would love to have every citizen be happy and content with each policy decision and each country we interact with agree with and adhere to alliances and sanctions that are agreed upon however... the world is not ideal.  The real story is that each country and each citizen within that country act rationally according to their personal disposition and belief.  There is no way in anyone's mind that those beliefs are going to match up and although there is a strong correlation between the belief system for the larger mass of citizens there are still differences that (as we have seen over the past decade) can escalate into culture wars and sometimes lead to civil wars.  It is imperative to understand that realism is the dominant theory that is applied to politics in this sense and the reasoning is logical.  Although most politicians and institutions will use euphemisms to describe hot topics or controversial issues, behind the smoke screen is a very realistic point of view and if we dig deeper almost everyone (excluding the outliers or extremists on both sides) has the same goal in mind the means to that end are the differences.
If every nation viewed the world ideally, there would be very little cooperation because it would be chaotic to try to comprehend why those from other nations are acting irrationally according to our personal perception of them and vice versa.  Idealism is a theory that NGO's use to try to gain influence and power because it "sounds" acceptable and less harsh but in reality, the world is a harsh place and it comes down to those who have the power and those who do not.  The G-20 make most of the world economic policy decisions because they have the resources to provide for their personal benefit which typically benefits other nations as well but countries are always looking out for number 1 because they have to.  That is key to survival and that is why idealism as a theory, would never work in a worldwide arena.  There are too many opposing views and beliefs that come into play, hence realism dominates.
This is something that has been on my mind over the past week or so as different news headlines have been debated and topics in class have circled these very issues.  I hope you can make a rational decision for yourselves after researching further what has been stated in this particular post.