00:48 - Source: CNN
Donald Trump: Hillary, she's not a New Yorker!

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"@HillaryClinton was angry + defensive the entire time," Priebus tweeted

Clinton campaign response: "That's just what taking the office of President seriously looks like"

Washington CNN —  

Republican National Committee Chairman Reince Priebus slammed Hillary Clinton Wednesday for seeming angry and not smiling more during a national security forum.

“@HillaryClinton was angry + defensive the entire time - no smile and uncomfortable - upset that she was caught wrongly sending our secrets,” he said in a tweet about the “Commander in Chief” forum hosted by NBC.

His tweet was swiftly criticized on social media for being sexist.

The Clinton campaign quickly responded to his tweet: “Actually, that’s just what taking the office of President seriously looks like.”

And her communications director, Jennifer Palmieri, who previously served at the White House, tweeted: “People. Reince actually said HRC needed to smile more. This is real.”

Robby Mook, Clinton’s campaign manager, said the fact that Priebus focused on her demeanor rather than her answers was telling.

“The fact that the only criticism they could have for Hillary Clinton is that she didn’t smile enough at a very serious forum on our veterans, on our national security and on the job of commander in chief just tells you everything you need to know,” he said Thursday on ABC’s “Good Morning America.”

Clinton and Trump both answered questions from NBC’s Matt Lauer and members of the audience during event focused on national security issues.

The issues from the Iraq War and veterans’ health to Clinton’s email use and Trump’s statements about Vladimir Putin and sexual assault in the military.

CNN’s David Wright contributed to this report.