Quoth R. Haag (2010, p. 280):

K. O. Friedrichs once took me to the home of Richard Courant to introduce me to his former teacher. I remember vividly one remark by the old master because I was at first thoroughly shocked and thought much about it. So I can still remember it almost verbatim: “There is a fascist group of mathematicians in Paris who have not understood that mathematical reasoning is a natural activity of the human mind.” Among my mathematical friends the work by the group which published under the pseudonym Bourbaki was very highly regarded and I was full of admiration for this unselfish collective effort at organizing all mathematical knowledge in logical order and elegant economical formulation. Why on earth did Courant classify this as fascist?

(One can find toned down versions of this — not naming Bourbaki — in Courant et al. (1962) or his NYU colleague Morris Kline’s “tirades” against the “modernists”.)