Glasgow Cathcart MSP James Dornan was left stunned after receiving the message and has forwarded the hate mail to police.
The flier has been circulated promoting the plans for violence on 1 May.
The poster, which is titled “Smash a Fenian Day’, has been produced anonymously.
Mr Dornan said: “It’s hard to believe someone who is intelligent enough to type something like that would be stupid enough to think it’s a good idea.
“It’s a very tiny minority who try to ruin the good name of the vast majority of people in this country.”
The circular says on the date of 1 May “we urge all protestants to stand up and put all fenians back in their place as it is time for our religion to fight the plastic Irish in our country”.
It does on: “These Fenian b******s have infiltrated our society, our councils and our government as well as high ranking officials in law.”
Points are said to be awarded in the circular for various acts of violence, including burning down a chapel, shooting, stabbing and punching.
‘Triple Bill’ acts perpetrated on a “Fenian, Scottish Nationalists and a Muslim” are also said to be worth extra points.
The sectarian flier was labelled “shocking” and “vile” by Scottish transport minister Humza Yousaf.
Mr Yousaf tweeted: “Shocking. Vile stuff. All it takes is one person to act upon this and folk will get hurt.”
The circular carries the image of the Union Flag.
It finishes with the message: “We will be mastered by no fenian b*****d. No surrender ever. F*** the Pope.”
There is concern the flier is a copycat of the ‘Punish a Muslin Day’ message, which has reportedly sent to addresses across the country and circulated on social media.
Counter-terrorism police are treating the letters as a possible hate crime.
The issue was to be discussed at the Scottish Parliament yesterday by a new cross-party group aimed at tackling racism and Islamophobia.
Police Scotland have not commented on the latest circulation.