Louise Morton, vice chairwoman of Labour’s Moray branch and mother of Fochabers and Lhanbryde councillor Sean Morton, referred to “Yes voting fascists” on Twitter.
The bizarre remark, posted at 5.33am on July 3, triggered an online row, days after a Labour candidate in Angus posted a picture of the Hitler Youth.
SNP MP Angus Robertson questioned what action the Scottish Labour Party would be taking against Mrs Morton.
He said: “What is Labour doing about it?
“Do they think it’s all right that one of their office-bearers in the north of Scotland compared Yes voters to fascists?”
Councillor Morton, who is due to stand for Labour against Mr Robertson at next year’s UK elections in Moray, gave a passionate defence and said his mum had been “misunderstood”
He said: “I know my mum was getting some heat and terrible abuse online about it.
“She was referring to stories on social media about people calling themselves fascists attending Yes campaign events.
“She was not talking about all Yes voters. It’s a total misunderstanding. It was taken out of context.
“Anyone who knows my mother knows that she is not the monster they are trying to make her out to be. She is a good woman who loves her family and tries to do her best for the people around her.
“Angus Robertson, our Westminster MP, had been attacking her relentlessly for it, claiming that she called Yes voters fascists.
“She did not. She had been accused of being in the Orange Order and referred to stories about fascists that were reported to have been at Yes rallies.
“She is one of the most tolerant and open-minded people I have ever met - and I’m sure that local SNP councillors who have met her would agree.
“It was her who sat and held my hand as I sobbed telling her at the age of 15 I was gay and her that - behind my back - made sure everyone else around me accepted me too.
“The portrait they have painted of my mother - taking three words she wrote online completely out of context and then demonising her - is simply not one I recognise. She did not deserve this.
“I know that if I was to ask anyone in politics they would tell me not to speak up, to keep my head down.
“They would tell me not to defend my mother because it wouldn’t make sense politically. Well, I don’t care. I wasn’t brought up to turn my back on the people I love.
“My Mum didn’t sign up to fight against Angus Robertson - I did. Angus has dedicated his life to nationalism.
“I want to dedicate mine to making sure people don’t have to struggle the way my Mum did.
“So let’s put an end to the point-scoring and this destructive gutter politics. And let’s keep our families out of it.
“Angus can make his case and I will make mine. I will do it with respect and civility. I hope he can do the same.”
A Scottish Labour spokesman said: “We expect all sides of the debate to act properly and respectfully and recognise that we must all work together the day after the vote to make the most of the decision people make.
“That is the message we have given to our members and we hope the Yes side are willing to do the same given the abuse we have seen from nationalists.”
A spokesperson for Yes Scotland said: “Abuse, no matter where it comes from is unacceptable and we don’t want it to detract from the high quality debate we are having in Scotland.
“We implore people on both sides of the debate always to express their opinions in a reasonable, respectful and courteous manner.”
Kathy Wiles, who had been selected to fight the Angus constituency for Labour at next year’s general election, resigned last week after tweeting an image of a group of children standing under a flag with an eagle and a swastika on it.