The former special forces soldier called the insult, which came from a satirical cartoon on the One Nation leader's X account, a "massive slur" on veterans across the country.
He retaliated by calling Senator Hanson "glass-jawed", branding her and One Nation MP Barnaby Joyce "lying cowards" after she refused to take down the offending sketch and said he was a "wanker".
Tension between the two politicians stems from the Liberal MP testifying during the defamation trial of now-accused war criminal Ben Roberts-Smith, who Mr Hastie served with in the SAS.
Opposition Leader Angus Taylor was the most prominent figure to spring to Mr Hastie's defence on Thursday, touting his colleague's military record and again demanding the One Nation leader remove the video.
"Andrew Hastie has served this country with distinction as an officer in the SAS. She should take it down," Mr Taylor told reporters on Thursday.
Later, during a speech prior to Question Time commemorating the 25th anniversary of the September 11 attacks, the Liberal leader again alluded to Mr Hastie's service during the global War on Terror.
"I take this opportunity to acknowledge all our war fighters who served ... in that necessary and noble cause over many years, patriots like the members for Canning (Mr Hastie)," he said.
An unlikely coalition of politicians, including staunch adversaries, has also stood up to defend the conservative Liberal frontbencher.
"I think how Pauline Hanson has treated Andrew Hastie is appalling," Labor minister Madeleine King told News24 on Thursday, echoing calls for the senator to take down the video.
The attack on a decorated member of the Australian Defence Force was "despicable", she said.
Ms King condemned the One Nation leader for backing away from the traitor label on Wednesday, when she said the cartoon was satire and accused Mr Hastie of "making a mountain out of a molehill".
"She's just got this habit of gaslighting ... what she is doing is accusing someone of one of the most serious things you possibly can," she said.
Fellow army veteran and Tasmanian senator Jacqui Lambie also took issue with Senator Hanson's comments.
"That woman is nothing less than a bloody coward," she told ABC Radio.
"She always has been, and she always will be. She wouldn't last one day in that goddamn uniform.
"Those cartoons (are) absolutely disgusting. They are full of bloody violence."
Greens senator David Shoebridge, who declared he would "go out and fight Hastie on pretty much every one of his political opinions", also offered Senator Hanson an impassioned rebuke.
"I can't work out how any political party can stand by an attack on somebody because they go into court and they tell the truth as they understand it," he told News24.
"It's actually pretty f***ing disgraceful."
The spat comes as the coalition seeks to nullify a surge in support for Senator Hanson's populist party, which has split much of the right-wing vote, particularly in regional and rural Australia.
The WA state seat of Secret Harbour, which sits squarely within Mr Hastie's federal seat, was the latest to flip to One Nation at a by-election in August, as the anti-immigration party eyes coalition-held electorates.
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