Recep Tayyip Erdogan is burning more of his bridges to the West. The Turkish strongman over the weekend escalated his war of words against Europe and especially Germany, his country’s most important ally. “When we call them Nazis, they [European leaders] get uncomfortable,” he said. “They rally together in solidarity. Especially Merkel,” meaning German Chancellor Angela Merkel. He went on: “But you are right now employing Nazi measures. Against who? My Turkish brother citizens in Germany.”

The dispute flared this month following the cancellation of a rally in Rotterdam, in the Netherlands, at which Turkish Foreign Minister Mevlut Cavusoglu was due to speak. The gathering was intended to encourage Turkish expatriates to vote “Yes” in an April referendum that would vastly expand Mr. Erdogan’s presidential powers.

The owner of the Rotterdam venue where the rally was scheduled backed out voluntarily, though Rotterdam’s mayor later suggested municipal authorities would have nixed it on safety grounds. Mr. Cavusoglu vowed he would show up anyway, prompting the Dutch government to deny him landing rights.

Mr. Erdogan reacted by calling the Dutch “Nazi remnants” and “fascists,” and he used similar epithets after two German municipalities withdrew permission for pro-Erdogan rallies, citing security and logistical concerns. “Your practices are not different from the Nazi practices of the past,” he said.

Also Sunday an Erdogan spokesman accused Germany of abetting July’s attempted military coup in Turkey. Compounding Berlin-Ankara tensions over the expat rallies is the arrest in Turkey of Deniz Yücel, a Turkish-German dual citizen and correspondent for the German newspaper Die Welt. Turkish prosecutors have accused Mr. Yücel of terrorist propaganda and incitement to hatred because he interviewed Kurdish militants and reported on alleged email hacks of Mr. Erdogan’s son-in-law.

Mr. Erdogan has banned more than 100 media outlets since the summer, but Mr. Yücel is the first Western journalist to face prolonged detention. A Journal reporter was detained for three days over the New Year and allowed to leave the country.

Mr. Erdogan’s rhetoric is driven by genuine anti-Western fervor as well as the need to fire up popular sentiment ahead of next month’s referendum, with polls showing a close contest. The President is accelerating his drive toward authoritarianism and he no longer bothers with the “moderate-democrat” pretense that once won admiration in Europe and the U.S.

Ms. Merkel has struck back rhetorically, but that may not be enough. The EU should consider withdrawing the visa liberalization and invitations to Mr. Erdogan to attend European Union summits that the bloc promised to Ankara in exchange for Turkey stemming the flow of Middle Eastern migrants into Europe. It is in Turkey’s self-interest to control its own borders, especially to stop terrorists from Syria, and that doesn’t warrant a perpetual diplomatic reward.

Revisiting that deal would weaken Mr. Erdogan’s message to Turks that he can bully Europe without consequences. Mr. Erdogan might escalate by trying to flood Europe with more refugees, but that’s why the EU shouldn’t outsource border enforcement to an erratic Turk whose promises can’t be trusted.