Bernie Sanders said on CNN's "State of the Union" Sunday that it is "disgusting" and "unspeakable" that a man unfurled a Nazi swastika flag during his rally in Phoenix last week.

Why it matters: Sanders, who lost family members in the Holocaust, could become the first Jewish presidential nominee of a major American political party.

The man, identified by the Anti-Defamation League as white supremacist Robert Sterkeson, had the flag snatched out of his hands and was escorted from the rally.

Sterkeson is a self-described "stunt activist" known for harassing Jewish and Muslim organizations and events and posting about it online, per the ADL.

What he's saying:

"We have been disrupted by various groups. Some Trump people have gotten excited and we've gotten rid of them. But the idea that there was a swastika — a symbol of everything that this country stands against. We lost 400,000 people fighting that symbol, fighting Nazism. Six million Jews were killed. Other people were killed. ... Obviously it is unspeakable. It is disgusting. I've got to tell you, I never expected in my life, as an American, to see a swastika at a major political rally. It's horrible."

— Bernie Sanders

Go deeper: Bernie's historic Jewish fight