William Butler Yeats was not a liberal, but in these lines, he offers a somewhat sympathetic, but peculiarly devastating, critique of liberal values. Liberalism is regarded here as a general outlook rather than a specific set of political ideas or objectives, and its fatal flaw is its openness to debate and correction. The liberal is always willing to consider his or her opponent's point of view. A particularly sympathetic and generous liberal will want to go beyond this and try to see the virtues and strengths of that point of view, understanding, respecting, and perhaps conciliating his or her opponent and always trying to find common ground.

On the other hand, although the example is something of a cliché, if you watch one of Hitler's speeches, perhaps the first words that come to mind will be "passionate intensity." Extremist groups, Fascists, white supremacists, and terrorists tend to be absolutely rigid and certain of their position. When you think about it, this is only to be expected. A terrorist who was open to reasoned argument and critical thinking would probably stop being a terrorist fairly soon. The type of people who persist in extreme views have to be "full of passionate intensity," just as intelligent, compassionate people have to be open to change. However, Yeats is skeptical, or perhaps cynical, enough to see that the people he describes as "the best" are not as robust as they might be in defending civilized values.