Sen. John McCain (R-AZ) on Monday invoked the violent weekend in Charlottesville, Virginia in order to show his support for National Security Adviser H.R. McMaster.

McMaster’s character has come under attack recently from various online personalities and outlets aligned with the so-called “alt-right,” a movement of misogynists and white supremacists birthed in online message boards like 4chan.

“I have had the pleasure of knowing General H.R. McMaster for many years, and greatly respect and admire his outstanding service to the nation,” McCain said in a statement. “The recent attacks upon him from the so-called ‘alt-right’ are disgraceful.”

“I hope the President will once again stand up for his national security adviser and denounce these repugnant attacks, which arise from the same purveyors of hatred and ignorance who precipitated the recent violence in Charlottesville,” he added.

McMaster is largely seen as having positioned himself opposite chief strategist Steve Bannon as a voice in President Donald Trump’s ear. Breitbart News, the conservative website Bannon once ran — and which he praised as “the platform for the alt-right” in July 2016 — has come out strongly against McMaster in recent weeks.

And Mike Cernovich, a popular conspiracy-minded journalist and provocateur, has alleged without evidence that McMaster has a drinking problem.

One reported Bannon ally and an a former member of McMaster’s National Security Council, Rich Higgins, was fired in July over a memo linking “globalists and Islamists” and “cultural Marxists” as part of a wide-reaching plot to undermine Trump’s presidency, the Atlantic first reported on Aug. 2. Trump voiced his support for McMaster in a statement on Aug. 5.

Various white supremacist groups and others affiliated with the alt-right protested in Charlottesville on Saturday against the removal of a statue of Confederate Gen. Robert E. Lee from a park. One man who had earlier been photographed with a white supremacist group was detained after allegedly ramming his car into a group of counter-protesters, killing one and injuring at least 20.