The man, Ray McGovern, is a 71 year old retired CIA analyst. He was reputedly standing up facing away from her in silent protest regarding her speech. He was blind-sided by security forces and forcefully taken away. This occurred within plain sight of the Secretary of State while she was speaking. She did a splendid job of not interrupting her message despite this silent objector being dealt with. She even had the poise necessary to ignore his lone cry of "Is this America?". Without missing a beat she managed to deliver her message with great aplomb.
Thankfully we live in a tolerant nation where people have the right to speak freely and not have their pleas ignored by the reigning government. In the US, everyone has a voice in how the government operates and the participation of the masses should be a shining example of what can be achieved when everyone works together.
/sarcasm: If this doesn't scare you, nothing will. This man was silently protesting Mrs. Clinton and facing away from her when he was attacked by security guards. His actions may be considered rude, but if you were to silently face away from someone and their friends attacked you, all kinds of legal actions could be taken (unless you are Hillary Clinton of course).