A Rainworth support worker who made indirect threats against his partner's ex-husband was labelled "jealous and possessive", a court heard.
Simon Rowland had been in a six-month relationship with the woman, but "didn't like the fact she still got on with her ex," said prosecutor Donna Fawcett.
"This culminated in a fracas between him, his partner and her ex-husband on December 20. He was warned about his behaviour after he was found banging on her doors.
"Since the warning he has continued to contact and text her, pleading with her to get back together again."
But on December 28, Rowland sent her a Facebook message warning "it's about time he put into practise a threat to have her ex beaten-up," said Ms Fawcett.
In a statement, Rowland's ex-partner said: "He has been told to leave me alone by me, his family and the police, but he still keeps carrying on.
"I just want him to leave me alone and I am willing to go to court."
Michael Little, mitigating, said Rowland, who had no previous convictions, is a support worker who helps vulnerable adults, and had no contact since December 28.
District judge Jonathan Taaffe said: "That's clearly a career that requires a great deal of time and dedication and thought to others.
"Quite the opposite of your behaviour in relation to this lady. She has a right to live her life - whatever your views on the rights and wrongs of her relationships with other people."
He fined Rowland £300, with £85 costs and a £30 government surcharge, and imposed a two-year restraining order, banning him from all contact.
Rowland, 29, of Thoresby Road, admitted harassment without violence, when he appeared at Mansfield Magistrates Court, on Wednesday.