A 49-year-old man filmed himself burning clothes belonging to his ex-partner and then posted the clip on Facebook.
Blackburn magistrates heard John Andrew Stevenson had acted out of frustration over problems with child access.
But the chairman of the magistrates told him his behaviour was not acceptable.
“Nothing will ever be resolved by taking matters into your own hands,” he said.
Stevenson, of Manor Road, Clitheroe, pleaded guilty to damaging clothing worth £300 belonging to Gemma Gawthorpe.
He was fined £50 and ordered to pay £45 costs.
Catherine Allan, prosecuting, said the Facebook clip showed Stevenson pour petrol onto the clothes and set fire to them.
“In fairness to the defendant, Miss Gawthorpe has contacted the prosecution and said he has replaced the clothing,” said Miss Allan.
“She said she was not minded to proceed with the case but that is not a decision for her.”
Stevenson, who is subject to a restraining order, told the court there were ongoing problems with access to his child and Miss Gawthorpe turning up at his home, which put him in breach of the restraining order.
“It seems that if I don’t do as I am told I don’t get to see my child,” he said.
“I was just frustrated about the situation.”