Hillgrove cat farm protester Rebecca Green was jailed for 12 months for "terrorising" farmer Christopher Brown and his family.
The 20-year-old animal rights campaigner was among 600 people involved in a violent demonstration at the controversial cat breeding farm, in Minster Lovell, near Witney, on April 18.
She admitted violent disorder after being caught on a police video hurling mud and stones at the farmhouse where Mr Brown and his family were hiding.
Oxford Crown Court heard that Green, from Winchester, had no previous convictions and "a good job".
Her barrister, Miss Helen Fields, pleaded with a judge not to send her to jail, saying she had been "swept up" in the protest. But the Recorder Michael Challinor, said he wanted to "send a clear message to others."
Sentencing Green to 12 months in jail, he said: "You were taking part in a very violent incident that involved in particular throwing stones at someone's home.
"Anyone who is on the receiving end of that sort of disorder knows the terror it can produce.
"I want to let others know that whatever their beliefs are, that if they take the law into their own hands with mob rule they will go to prison."
Earlier, Mr David Bright, prosecuting, described how Mr Brown and his family were terrorised after protesters began breaking down the fence surrounding his home.
Mr Bright said: "There seems to be some misconception that Mr Brown and his family are cruel, which they are not."
A fellow protester shouted "no surrender" as Green was sent down.
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