A follower of Charles Maurras, Bainville was a founder of Action Française and soon became an important figure in the Institut d'Action Française, a college of sorts ran by the organisation (it had no permanent buildings but ran lectures and study groups where possible).
Bainville became notorious in French political circles for his Germanophobia and this was one of the defining strands of his writing. His early works suggested that the history of Europe was defined by the struggle between the superior French civilisation and the barbaric German kultur. His Histoire de deux peuples (1915) underlined the importance for France of German weakness and sought a return to the pre-Franco-Prussian War status of Germany. His Les Conséquences politiques de la paix (Political Consequences of Peace, 1920), whilst intended as an answer to John Maynard Keynes' views on Treaty of Versailles, was actually translated into German in Nazi Germany and presented as evidence that France had a mission for German destruction. His other written works included Histoire de France, as well as political columns for a number of newspapers and editing La Revue Universelle for Maurras. He was however an admirer of Italian fascism and when early reports came through about violent acts by Benito Mussolini's fascio in 1921 he praised it as proof that Italy was regaining her strength.
Bainville was appointed to a chair at Académie française in 1935, although he did not hold the position long as he died soon afterwards. A strong Catholic, he was denied the last rites by Cardinal Jean Verdier as the Pope had condemned Action Française in 1926. Nonetheless the sacrament, as well as his funeral, were performed by a canon who was sympathetic to the movement. Bainville's funeral proved a further source of controversy when Léon Blum was set upon by a crowd of mourners during the funeral procession.