Two men have been handed fines for posting sectarian messages on Facebook.
Matthew McKenna, 20, and Dean Boyd, 21, whose partner and child are Catholics, threatened to kill all taigs and wrote other religious abuse.
It was during the height of the loyal order marching season in Co Antrim last summer, when tensions traditionally run high and can degenerate into violence.
Boyd was fined £250 and McKenna £400.
It was reported to police by Sinn Fein Northern Ireland Assembly member Daithi McKay, who was named by McKenna in one post and who told officers he feared for his family's safety.
Coleraine Magistrates' Court district judge Richard Wilson said they were stupid and rabble-rousing remarks.
"I hope you realise how inappropriate and stupid your comments are.
"It is comments like this that excite and exacerbate any tensions within this community and we can well do without it," he said.
This is believed to be one of the first cases of its kind in Northern Ireland of prosecution for a social networking offence. There have already been several in Great Britain, including a man convicted of sending racist messages about a footballer who was seriously ill.
Both accused pleaded guilty to sending a message which was grossly offensive or indecent.
Boyd logged onto the social networking site on his 21st birthday on August 25 last year.
He is an unemployed father-of-one from Skye Park, Ballymena, and has a partner and baby who are Catholics.
Boyd's post said: "kill all taigs" and "f**k the Pope", a prosecutor told the court.
A lawyer for the defendant, who expressed remorse in court, said he had quickly removed the offending post.
His solicitor said it was his birthday and he had taken drink.
There were a number of messages being passed and other people's comments were "much more serious", the lawyer said.
He added: "Mr Boyd did post the comments that have been read out but within 20 minutes he realised he should not have done such a thing and took the comments down.
"He was extremely frank and remorseful to police, in contrast with the responses of the other individuals."
He said: "He runs in mixed circles and his friends heard of this and he suffered quite a deal of appropriate opprobrium for what he has done."
He said he has nothing to do with the other individuals posting messages.
McKenna, 20, a factory worker from Lisnahilt Road, Broughshane, Co Antrim, also appeared today.
A prosecution lawyer said he made a comment which named Mr McKay.
McKenna also said: "Let's show the scum in Rasharkin (a Co Antrim village where many Catholics live) how it is done.
"God save the Queen. For God and Ulster, Kill all taigs. Lest we forget."
His lawyer said he did not realise the comments were public.
The magistrate condemned the abuse.
"These stupid, rabble-rousing sentiments are better left unsaid and your mouth zipped," he told McKenna.
"When you place them on the media like this it only excites and stirs up feelings in the community, which we could all do without."
Mr McKay said: "No-one would get away with making such comments in the street and it is important that a message is sent out that sectarian comments and threats such as this are not acceptable and in this instance can inflame tensions.
"Sectarianism is a scourge on this society and all sectarian death threats that are made in any context need to be taken seriously."
There has been inter-communal trouble over many years in Co Antrim, with Catholic churches targeted by arsonists and attacks on orange halls as well as protests and counter-demonstrations at loyal marches.