
“A liberal is a man too broadminded to take his own side in a quarrel.”
An earlier unattributed version of this quip appeared in What Man Can Make of Man (1942) by William Ernest Hocking: "He lends himself to the gibe that he is 'so very liberal, that he cannot bring himself to take his own side in a quarrel.'" http://www.barrypopik.com/index.php/new_york_city/entry/a_liberal_is_a_man_too_broad_minded_to_take_his_own_side_in_a_quarrel/
Source: As quoted by Guy Davenport (The Geography of the Imagination) at page x in A Liberal Education http://books.google.de/books?id=Dly0RgUc0YcC&pg=PR10&dq=A+liberal+is+a+man+too+broadminded+to+take+his+own+side+in+a+quarrel.&hl=de&sa=X&ei=Xt_OUZSGJcjLswaApYDQBg&redir_esc=y#v=onepage&q=A%20liberal%20is%20a%20man%20too%20broadminded%20to%20take%20his%20own%20side%20in%20a%20quarrel.&f=false by Abbott Gleason (Cambridge, Massachusetts, USA, Tide Pool Press, 2010).
Source: As quoted by Harvey Shapiro “Story of the Poem”, 15 January 1961, New York (NY) Times, Section SM page 6 https://www.nytimes.com/1961/01/15/archives/story-of-the-poem-the-story-of-the-poem.html?searchResultPosition=1