As the Michigan primary was underway, "JackAM" host Jack Allison approached Jansing at the Detroit Institute of the Arts (DIA) and asked her why the network chose not to dedicate any significant coverage to the disrupter who flew a Nazi flag at Sanders' rally in Arizona last week.
"Hi, can I ask you a question?" Allison asks. "Why did your network not find it newsworthy to report on an anti-Semitic attack [at] the Jewish candidate's rally on Friday?"
"[I] don't make those decisions. So I can't answer that," Jansing responds.
"So who makes those decisions? Because I texted producer Daniel Arnall personally and told him about this information, so it's not credible that no one in the building knows. So I want to know why the network made that decision," Allison continues.
Allison, an open supporter of Sanders who was in Michigan canvassing on the candidate's behalf, accused Jansing and the network of "crafting a narrative."
Jansing then tells Allison, "I don't like your attitude" and "I don't appreciate you harassing me."
In the video, at least one man whom Allison describes as a "security guard" is seen standing between him and Jansing. Before the video ends, Jansing is seen reaching for Allison's phone.
Speaking to Fox News, Allison alleged that Jansing "gripped my phone as hard as she could and tried to take it from me" and ordered, "Don't film me without my permission." He then claimed that he was put in a "headlock" by what he thought were two MSNBC security guards.
Allison explained that he had previously texted Arnall, an NBC News executive producer, about the person who had flown the Nazi flag at the Sanders rally, but Arnall had "blocked" his phone number.
After the altercation, Allison told Fox News he was escorted out of the building but later returned hoping to resolve the encounter, but a DIA staffer told him that the MSNBC team was "not interested in speaking," which prompted him to file a police report to officers from Wayne State University, which will be directed to the Detroit Police Department.
Allison said he plans to press assault charges against Jansing and the security guards.
While he admitted he was "firm and anxious" during his exchange with Jansing, Allison claimed the incident reflects on the network's wider coverage of Sanders during this election cycle.
"I do think MSNBC has had an anti-Sanders bias -- this is the network where multiple anchors have made references to Sanders supporters as Nazis," Allison told Fox News. "The coverage has been uneven for the duration of the primary, but since the moderate wing coalescing around Biden, I think MSNBC has engaged in a truly irresponsible [...] media campaign to get Joe Biden through the primary."
The progressive Twitter personality slammed the network for dedicating overwhelming coverage of remarks made by recent 2020 dropout Sen. Elizabeth Warren, D-Mass., who criticized Sanders' online supporters, while "only one show" covered the anti-Semitic attack "briefly," he said.
The incident, which was reported on NBC News' website, was mentioned on "All In with Chris Hayes," as well as the MSNBC weekend program "AM Joy."
"I believe that MSNBC didn’t cover this attack because it didn’t fit the 'Bernie Bros are uniquely toxic' narrative they’ve been building in the lead-up to today’s primaries," Allison said. "MSNBC didn’t cover this story because they decided it wasn’t newsworthy. I think that’s offensive, and given what we know from 'Catch and Kill' about the journalistic practices at NBC, I think we should know how and why that decision was made."
"Catch and Kill" is a reference to 2019 reporting from Ronan Farrow, who alleged that NBC News buried the Harvey Weinstein scandal in order to shield the network's star anchor and alleged sexual predator Matt Lauer.
MSNBC did not immediately respond to Fox News' request for comment.