Sen. Bernie Sanders (I-Vt.) stuck up for Democratic presidential rival Hillary Clinton on Sunday, calling some criticism of the former secretary of state "sexist" and opportunistic.

"I think for a variety of reasons, Hillary Clinton has been under all kinds of attack for many, many years," Sanders said during an interview with CBS's "Face the Nation."

"In fact, I can't think of many personalities who have been attacked for more reasons than Hillary Clinton. And, by the way, let me be frank — and I'm running against her: Some of it is sexist."

The comments came in response to a question about Clinton's private e-mail server and whether her handling of the controversy surrounding her e-mail raises questions about her trustworthiness.

Sanders declined to criticize Clinton on the issue.

"I don't know that a man would be treated the same way that Hillary is," he said. "All that I can say is I have known Hillary Clinton for 25 years. I admire her. I respect her. I like her. She and I have very different points of view on a number of issues."

Sanders was in Seattle on Saturday for two campaign speeches, one of which was scuttled after Black Lives Matter protesters took over the stage. Activists against police brutality have argued that Sanders has not done enough to call attention to the issue.

Later in the day, Sanders drew a crowd of 15,000 people for his second speech, his biggest audience yet.

The CBS interview did not address either speech.

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