Realism Case
To me the reason that realist place so much emphasis of security is simple. If they feel secure they will be more inclined to trade and coexist with another nation or two. This just states the facts and that is cooperation is not the key, the key is to make as many allies as possible that serve your needs and still maintain security.
Realism in fact has been a reality for the entire existence of the world, as there has never been total peace and that I am sad to say will never change. On a side note you can always look to the fact that no two democratic countries have ever fought a war against each other directly. The reason I say directly is because behind the scenes support such as money guns and other actions have been supported by democratic nations just not publicly. Another fact is no nation has came to the aid of another nation simply because it cared for that nations well being, all help is geared toward the hope of obtaining something in return. For an example just look to the Iraq conflict, do you think we would have cared if oil was not at stake? I think not and if you do you are fooling yourself. Security is a founding block for the any and all nations and they can accomplish this by being economically sound. As we all know having a strong economy always gives a great deal of security all by itself. When the economy is flourishing why would anyone push the button to cause it to go south? A nation has always been its own provider of security.
Threats against any state will only stands to increase its own security. Any threat can be used to take away rights by the guise of it helping you as a citizen remain or get more secure. A perfect example of this would be 911, after that day the United States has implemented several laws under the guise that it would better protect us from future attacks. That case is still out for judgment; I think the new laws only took away several rights that we had as Americans. All it did