Gavin Doig, prosecuting, said Henderson wrote to the fake profile saying he wanted to kiss her “neck, shoulders and tummy button”.
But Mr Doig said Henderson stated he was prepared to wait until the girl was ready to take things further.
The prosecution said Dark Justice’s responses were “tempting Mr Henderson to express intentions to go further than he himself is expressing an interest in doing”.
Dark Justice were described as “Machiavellian” by a barrister defending Henderson, who admitted grooming and then trying to meet a 13-year-old girl.~
“However, it is undoubtedly a serious offence,” the judge said.
Henderson was handed a three-year community order with rehabilitation requirements.
The judge said: “I hope you will never bother a court again. I am perfectly sure you will learn from this unfortunate experience.”
Henderson must register as a sex offender for five years.
Outside court Dark Justice said: “We don’t entrap people. It was his choice to come to Newcastle.
“Look at all the investigations we have carried out. If we were that dishonest, why didn’t he plead not guilty?”
Dark Justice have helped to secure almost 40 convictions in the two years they have operated.