The RSL has added to calls for party leader Pauline Hanson to take down the cartoon video, which remains pinned to her X profile.
The tension between the Liberal MP and Senator Hanson stems from him testifying during the defamation trial of now-accused war criminal Ben Roberts-Smith, who Mr Hastie served with in the SAS.
Defence Minister Richard Marles said the video from One Nation was tasteless and Senator Hanson needed to clarify why the comments were made.
"It is utterly tasteless, and no one should be using that word in respect of any veteran," he told ABC TV on Friday.
"(Traitor's) not a word which should be associated with people who undertake that service.
"It's an insult to all veterans."
Senator Hanson on Wednesday denied calling the Liberal MP a traitor, saying it was only a satirical cartoon and he was "making a mountain out of a molehill".
RSL Australia said Senator Hanson's video went beyond a political disagreement.
"When the word 'traitor' is thrown at someone who has worn the uniform and deployed on operations, that stops being politics and starts being an attack on every veteran's service," it said in a statement.
"Branding a former soldier a 'traitor' sends a corrosive message to the wider veteran community: that your service can be recast as betrayal the moment it's politically convenient."
One Nation Senator Sean Bell said the party stood by the cartoon.
"I don't think the party has anything to apologise for. I think people should go and watch the cartoon because I think in it there's a lot of very insightful things," he told News24.
"That cartoon has been out for a very long time. He has simply chosen this week to come into parliament, to do the rounds on media, to make things not about veterans but himself."
Liberal Senator Jonathon Duniam said Mr Hastie had the coalition's full support.
"(Ms Hanson) wants to lead this country. Well, then start telling us why you do some of the silly things you do."
