Despite Vietnam.
Charles P. Pierce explains (from a longer piece you should read!).
… [Attorney General Holder] gave his speech at the Lyndon B. Johnson Library in Austin. It so happens that it was on this very issue that LBJ gave the greatest speech given by an American president in my lifetime. Keep your “Ask Nots” and your shining cities on a damn hill; this was the real stuff — straight, no chaser. It came on March 15, 1965, in the aftermath of the bloody assault by Alabama law enforcement on the non-violent demonstrators who were attempting to march to Montgomery to demand their rights as citizens to vote for their leaders. These rights had been systematically denied for more than a century, often by force, but more often by the kind of bureaucratic trickeration and legal legerdemain that didn’t deny their rights outright, but that made it impossible for those people to exercise them. This always has been the subtle sabotage of the clever bigot. It came in a Southern accent, which was the most startling thing of all.
Johnson’s speech linked the civil-rights movement to Lexington and to Concord. It linked the freedom of black citizens to the freedom of all citizens. It called every bluff. It named every name. It brought every hidden sin into the light. It left no alibi standing. It closed every escape hatch. It asked America to be America, or to shut the hell up about it. …
“Every American citizen must have an equal right to vote.” LBJ March 15, 1965