Facebook has long banned white supremacy and other hateful treatment of people based on race and religion - but it hasn't applied the same rationale to white nationalism.
"We were initially thinking about broader concepts of nationalism and separatism such as American nationalism, Irish nationalism and Basque separatism," Mr Casseus said.
"But in speaking with many people in the civil rights arena, we were urged to reconsider our stance."
Senator Anning, who's been condemned for linking the Christchurch terror attack to Muslim immigration, will have content removed if it violates the new policy.
"In the case of Senator Anning, we will remove content if it violates our policy," a Facebook Australia spokesman told AAP.
"But we need to be mindful that (politicians) are in parliament and ... they have a right to political speech as part of that policy framework."
The Queensland politician has more than 110,000 Facebook followers.
The upper house is expected to censure Senator Anning when it reconvenes on Monday.
Mr Casseus suggested the company's response to politicians may be guided by parliament, pointing to an almost-unanimous motion in the US Congress in January that rebuked a member for his support of white nationalism.
"While there is disagreement about any hot button issue, we feel that we are in the right place," he said
"Regardless if you are a politician, we apply our policy consistently across the globe so that no matter who you are, or where you are, we strive for consistent enforcement."
Australian Catholic University Institute for Religion, Politics and Society senior research fellow Joshua Roose says the new policy will "shut down the shopfront" for those broadcasting white nationalist views.
But Facebook will have a hard task stopping memes, emerging trends and widely used symbols hijacked by white nationalists.
"Basically, (the ban will stop) people walking in the front door and then immediately engaging with a whole community of like-minded far-right extremists," he told AAP.
"But no doubt they'll pop up elsewhere ... and they will migrate to other platforms."
Australian experts weren't involved in the initial conversations about what content to ban but local experts will be meeting with Facebook this week.
"Local knowledge matters and there is a variety of expertise that needs to be drawn on," Andre Oboler, chief executive of the Melbourne-based Online Hate Prevention Institute, told AAP on Thursday.
Dr Oboler urged Facebook to fund civil society groups tracking extremist material after the platform said it would direct people searching for extremist terms to organisations that assist people to leave hate groups.
The half-trillion-dollar company says it isn't funding the groups at this stage.
The bans will begin in early April.