Thousands of supporters cheer and wave flags while listening to Turkey's main opposition Republican People's Party leader Kemal Kilicdaroglu speak on stage during the "Justice Rally" on July 9 in Istanbul. (Chris Mcgrath/Getty Images)

ON SUNDAY, Secretary of State Rex Tillerson praised the “brave men and women” of Turkey who “stood up against coup plotters and defended their democracy” during a failed coup attempt last July. He was right to do so. Unfortunately, he failed then to salute the brave men and women who have stood up against President Recep Tayyip Erdogan’s brutal purge of dissidents and independent media since the fizzled coup.

In ignoring the disturbing events of the past year, Mr. Tillerson may have been hoping to curry favor with the Turkish president before a crucial discussion on regional security. Turkey, jarringly, is an increasingly repressive nation but also a NATO ally; an Islamic-majority country growing increasingly hostile to secular liberalism but also a partner in the U.S. engagement in Syria. In other words, it’s complicated.

But complications don’t mean it is necessary, or beneficial, for the United States to toss aside its own ideals. Mr. Erdogan’s regime has grown steadily less tolerant. In April he engineered a referendum that polarized the nation and granted him a broad range of autocratic powers. Turkish authorities have suspended approximately 150,000 government workers and detained more than 110,000 people, including journalists, civil society activists and judges. Just last week, the director of Amnesty International Turkey and nine others were detained during a training session for human rights defenders, the latest in a long line of arbitrary arrests. Mr. Erdogan’s security guards even felt free to beat up protesters in the heart of Washington.

On the day that Mr. Tillerson arrived in Turkey, tens of thousands of citizens rallied at the end of a march for justice from Ankara to Istanbul. They, too, are brave men and women. Why not say so? Even a proponent of a “realist” foreign policy should understand that failing to show support for millions of democratically minded Turkish citizens is not in the United States’ long-term interest. And decades of precedent, during and since the Cold War, show that it is perfectly possible for U.S. diplomats to conduct serious business with autocrats while at least speaking up for human rights and the defenders of freedom, no matter how beleaguered.

The demonstrators who participated in the three-week-long march risked their safety and freedom to show Mr. Erdogan that his policies will not go uncontested. Mr. Tillerson’s dispiriting silence, by contrast, tells Ankara that it can continue its blatant assault on dissent at no cost in international standing.

The secretary’s statement was particularly disappointing given that the State Department had rebuked Turkey last week for its most recent round of arbitrary arrests. Such statements carry more weight when delivered in person — but Mr. Tillerson, at least publicly, opted not to make the delivery.

Mr. Tillerson has said he hopes to “mend” U.S.-Turkish relations, which soured during the final months of the Obama administration. This is important — but it can and should be accomplished without betraying democratic ideals and the people who are fighting on their behalf.