He was the leading literary critic of Action française and the author of the first work on Charles Maurras.
Part of his general argument, that the French romantics had damaged the concept of monarchy, was influenced from the side of the Action Française and Maurras.
That strand of anti-romanticism, close to that of the essayist Ernest Seillière and the counterrevolutionary tradition, later affected Carl Schmitt and his Politische Romantik of 1921.
Up to World War I, Lasserre was a militant, associating with Charles Péguy and digesting the ideas of Georges Sorel.
His colleagues Henri Massis and Alfred de Tard were concerned also at the perceived falling away of classics at the Sorbonne.