This actually seems to be happening - Americans opposed to US interventionism in Iraq are facing arrests, job losses, threats

"After Zinni challenged the administration's rationale for the Iraq war last fall, he lost his job as President George W. Bush's Middle East peace envoy after 18 months.

"I've been told I will never be used by the White House again."

Across the United States, hundreds of Americans have been arrested for protesting the war. The American Civil Liberties Union has documented more than 300 allegations of wrongful arrest and police brutality from demonstrators at anti-war rallies in Washington and New York."

...

"Internet chat rooms have spouted "tons and tons of vitriol aimed at us," says McArdle, a former network TV executive.
"Things like, `Tell me where Tim Robbins lives and I'll go bash out his brains,'" she says.
"Or, `If you don't like America, why don't you move to Iraq? Why don't you move to Canada?'
"The real backlash comes from the right wing, from America's talk radio guys — when their ratings are down — not from the industry," McArdle says. "We get the `You're either with us or agin' us.'"
Comes with the territory, she adds.
"We're a nation of dissenters."

...

"Peace scholar Stephen Zunes — so-named for winning a Peace and Justice Studies Association award for leadership in promoting such scholarship — says he was recently "uninvited" to speak to the Arizona state bar association despite a six-month-old commitment."