Sun Tzu's strategy says that you can only predict people's reactions if you understand their primary goals. It also says that you can only know people's true goals by judging their actions rather than their words. People have, or can claim to very different goals from those that truly motivate them. For example, this article by Senator Joe Lieberman discusses the fairly recent reversal in the traditional view of the Democratic Party regarding their view of national defense. Read the whole article about the history of the Democratic positions on national defense, but in the end, he sees the change in that policy as brought about by the core motivations of certain key elements in the party:

If the Democratic Party had stayed where it was in 2000, America could have confronted the terrorists with unity and strength in the years after 9/11. Instead a debate soon began within the Democratic Party about how to respond to Mr. Bush...When total victory did not come quickly in Iraq, the old voices of partisanship and peace at any price saw an opportunity to reassert themselves. By considering centrism to be collaboration with the enemy – not bin Laden, but Mr. Bush – activists have successfully pulled the Democratic Party further to the left than it has been at any point in the last 20 years.