The Prime Minister has continued to face questions over the appointment of the 27-year-old as one of top aide Dominic Cummings' team of "weirdos and misfits".
It emerged over the weekend Mr Sabisky he had called for mandatory contraception to prevent a “permanent underclass” and argued black people had genetically lower IQs than white people in online posts.
Number 10 refused 32 times to say whether the PM shared the views of his employee in a heated Downing Street briefing.
The Deputy Labour Leadership Candidate told the Mirror: “I think that what Johnson and Cummings are doing, is that they are testing the country.
“I actually think it’s very sinister that they are seeing what people find acceptable or not."
Ms Butler added: “I think this government is trying to desensitise people to injustice is trying to desensitise people and sew hatred and division.
"And we have to stand up against it.”
Speaking after Sabisky quit on Monday night, blaming "media hysteria" about his “old stuff online” for making him a distraction, Butler warned that the government is trying to "desensitise people".
“It’s exactly the same thing that, Toby young said, and why I spoke out about it in Parliament about him being given a position in the government in education and this is exactly why I spoke out about it."
Butler, who has served as the shadow women and equalities minister, said she "deliberately waited before commenting".
“I wanted to see whether people were going to be outraged about it I wanted to see whether his own ministers would say something about this because I really think it’s a test," she said.
“I think this government is trying to desensitise people to injustice is trying to desensitise people and sew hatred and division. And we have to stand up against it. And I also think that’s why having me as deputy leader frightens them so much - because who I am will confront their views.”
Asked what she thought about the response from the Tories, she described it as “absolutely shocking”.
Adding: “On the one hand you’ve got Priti Patel who says that racism doesn’t exist - shes’s our Home Secretary.
“You’ve go MPs who are Afro-Carribean, Asian, Indian, Pakistani - if you’re not outraged about the infiltration of racism and racists and pseudo-scientists at the heart of your government, there is something seriously wrong.
She says that the direction the Prime Minister and his adviser Dominic Cunnings are pushing the country in is worrying - and it's not where the British public are.
But people can't let this just wash over them.
“This is not the Britain that we live in and we should all refuse to allow Johnson to take us down this road - it is a sinister and dark path. "
“The biggest threat to our country is the rise of the far right. This is what they do they’re pandering to the rise of the far right.”
Butler explains that the recent deportations to Jamaica are "another test".
She added: "You hear about these things and then you read the United Nations report and it's like opening the blinds".
"What they will do is they will say 'everybody who has been deported are rapists and murderers' and so you're not going to defend a rapist or a murderer are you? So they get you worked up and then you find out that somebody came to the country aged 11 got convicted of stealing two mobile phones under joint enterprise which is now unlawful, got a higher than normal sentence because of institutional racism in the judicial system, and is now being deported to a country that they don't know aged 30 - 10/11 years after they committed a crime so you think 'oh, they're not all rapists and murderers'."
"They are trying to desensitise us to injustice and we have to be mindful of that - because you don't know when they're going to come for you.
"If we read somewhere we read somewhere that a government, state sanctioned hostility towards a marginalised group of people the United Kingdom, would be with the United Nations, sending people to that country to investigate.
"The hostile environment towards British citizens who were from Jamaica was state sanctioned hostility.
"You saw people who had their livelihoods taken away, their houses taken away, committed suicide. Who were made homeless and hungry, all because of the state who couldn't get medical help who died of cancer, all because of state sanctioned hostility. We're in quite a dark place face, and it's easy for us to just kind of, make it wash over our heads."
Butler has fought these battles for a long time - but it does not mean she is not ready for another fight.
"People forget - apart from my Mum she never forgets that I was a minister in a Labour government and I was the first black woman to stand at the despatch box and respond on behalf of Her Majesty's Government which is a big deal," she said.
Recently in her role as shadow women and equalities minister, she cites the introduction of a stand alone women's conference and the creation of the Bernie Grant leadership programme - designed to get more BAME candidates to stand for local and national government and named after the former Tottenham MP as achievements - but she says there is still work to do.
"I think there are so many barriers put in our way," she said.
"Even standing as deputy people tryig to speak for me as a black woman - it's so offensive.
"They say people don't put themselves forward and then you put yourself forward and get ignored."
She has served under four Labour leaders and refuses to define herself by any of them but it's her experience that she thinks marks her out.
"I don't really like all of these labels because I find them divisive but I'm a very proud working class, socialist with sensible views and values whose focus is to get us into government because there's no point in having great policies if we're never going to get into government.
"And that's why we need to have experience, and my kind of experience in the top team because I'm the only person who's ever served in a Labour government and it's vital".
She thinks it's her experience that's needed worrying that the two top positions in Labour should not be held by those who have never been in government.
“There are people that want to come back to us. What we have to do is we have to make sure there’s no reason for them not to.”
The veteran campaigner, who was first elected in 2005, admitted it was a "disappointment" that it was so hard to get enough MPs to back her.
She limped over the line with just enough MP nominations to go through to the second stage.
But she said there's a reason she lagged behind accusing the frontrunner Angela Rayner accusing her of launching her campaign a year ago when she should have been campaigning for a Labour government.
Asked why Rayner is so far out ahead, she said: "Of course she started her campaign early - a clever thing to do - wish I’d started it 12 months ago and started signing people up."
It's clear the MP does not lack confidence.
She says she wasn't surprised when a recent poll found her beating rivals on qualities including her charisma, how tough she is and how trustworthy.
Dr Rosena Allin-Khan was rated the highest for how "normal" she came across, how "in touch with ordinary people" and being "intelligent.
In contrast Angela Rayner did not score top for any of the measures despite storming ahead in the deputy leadership race so far.
"I know it surprised a lot of people, but not me," says Butler who, often gets recognised by people from sitting next to Jeremy Corbyn on the front bench.
“I’m playing catch up but the members are phenomenal," she said.
“And it’s not just a grassroots campaign. It’s an underground campaign, I mean this was serious stuff that’s happening.”
Butler has served under Blair, Brown, Miliband and Corbyn and is clear that she has not always agreed with everything those Labour leaders have done.
But she says disagreements should happen in private.
To her mind Labour would have been in government if the so-called coup -when MPs quit Jeremy Corbyn's shadow cabinet in 2016 -had not happened.
"If it wasn't for the coup we would have been in government, if we had been disciplined.
"Divided parties don't win elections, that's why I've never been under a coup, not under Blair, Brown," she said.
She says she prefers to hammer things out behind closed doors but that doesn't mean she doesn't get her way.
"What I've always done is I would have a one-to-one meeting, and I would lay my stall out and I would say this is why I'm doing what I'm doing and by the end of the discussion we come to considered position- which is normally my position because it's well thought out."
Smiling she says she wants to be “a John Prescott type deputy - but without the violence”.