Not many intellectuals paid the price for their pacifism as dearly as Russell did. Once, he was a social pariah for this reason only. Yet he composed these lectures in the hope of talking some sense into the young minds of Europe.
A core axiom of these lectures is the idea that humans are intuitive and impulsive. If the impulses cannot run their courses creatively, then tend to be destructive. This, to me, feels like a partial truth, or a truth that is too simple for the complex world we live in.
Even if the axiom is partially correct, the reasoning following this axiom can at least reduce destruction if not eradicate it. This is why these lectures are still relevant.
Russell explored the various forms of social institutions, their merits-demerits, and relevance to modern society in most of the lectures to understand what was wrong with WWI Europe. With a syndicalist, freedom-loving outlook his reasoning culminated in a call to create a better political theory as such:
Also published under the title of Principals of Social Reconstruction, and written in response to the devastation of World War I, Why Men Fight lays out Bertrand Russell's ideas on war, pacifism, reason, impulse, and personal liberty. He argues that the individualistic approach of traditional liberalism has reached its limits and that when individuals live passionately, they will have no desire for war or killing. Conversely, excessive restraint or reason causes us to live unnaturally and with hostility toward those who are unlike ourselves. This formidable work greatly contributed to Russell’s fame as a formidable social critic and anti-war activist.