"Dissent is the highest form of patriotism" is often attributed to Thomas Jefferson, but to date we have found no evidence that he said or wrote this. Its true origins are uncertain, but the saying may have entered popular culture during the Vietnam era.
The earliest usage of the phrase we have found is in a 1961 publication, The Use of Force in International Affairs: "If what your country is doing seems to you practically and morally wrong, is dissent the highest form of patriotism?"
The phrase was used repeatedly during the Vietnam era, and this may be when it came into general currency. On October 15, 1969, in a speech at Columbia University, Mayor John Lindsay of New York City stated, "We cannot rest content with the charge from Washington that this peaceful protest is unpatriotic...The fact is that this dissent is the highest form of patriotism."