Sanders said his wife and African American women in his campaign have faced ugly attacks as well. The Vermont senator called the internet the “Wild West” but argued that the vast majority of his supporters would never attack others and challenged other campaigns to be mindful of attacks from their supporters on his campaign.

“I have a hard time understanding, given my views, which everybody knows, how anybody who thinks they are supporting me would do some ugly and terrible things,” Sanders said.

He suggested that bots or people seeking to divide the progressive movement could be responsible for some of the messages from purported Sanders supporters.

“I am the strongest, perhaps lifetime, supporter of unions in the United States Congress. The idea that anybody who works with me would make a vicious attack against a union leader, just because we disagree on an issue, is incomprehensible to me,” Sanders said. “And you know what? I’m just not sure that that’s true.”

“And anybody out there — anybody out there who claims to be a Bernie Sanders supporter, we work with the unions,” Sanders continued. “This is a union-led campaign. We believe in unions. We will never attack union leadership, and we will not attack people on a personal basis. We can have a debate about the issues, but I do not believe in online bullying. End of discussion.”