The Liberal MP, Andrew Hastie, says Ben Roberts-Smith is entitled to the presumption of innocence but “none of us are above the law” in his first public comments since Australia’s most decorated living soldier was charged with war crimes.

Hastie served alongside Roberts-Smith in Afghanistan and was among the 21 Special Air Service (SAS) who gave evidence in the defamation case he brought against the Nine newspapers.

Appearing under subpoena by the newspapers, Hastie, who was then the assistant defence minister, told the federal court in 2022 that it was a “fairly well-established rumour” that Roberts-Smith had kicked an unarmed “PUC” (a “person under control” in military parlance) off a cliff in Afghanistan.

Hastie also told court that there was a “widespread view” within the SAS that Roberts-Smith was a bully and that he was no longer “proud” of a soldier who he once held in high regard.

The court ruled in the newspapers’ favour in June 2023, finding that Roberts-Smith had, on the balance of probabilities, committed war crimes in Afghanistan.

The Liberal frontbencher had not commented publicly since Roberts-Smith’s arrest at Sydney airport on Tuesday, as other Coalition MPs, as well as Pauline Hanson and Bob Katter, publicly criticised his treatment and the process that resulted in the five charges of “war crime – murder”.

Speaking with 2GB on Thursday, Hastie said the arrest was a “very sad and sobering day for the country and for many Australians”.

“I think Ben Roberts-Smith is entitled to the presumption of innocence. He’s entitled to a fair trial, and that’s why I’m very circumspect about making comment, because the last thing we want is for his trial to be prejudiced by political commentary,” he said.

In a broader message to veterans, Hastie said: “we all had a mission to serve our country, and 99% of us did our job with honour, and we did it in a war that was incredibly frustrating”.

“Anyone who was at the pointy end doing combat operations in Afghanistan knows that things never go right, and we often had to make very difficult decisions in difficult circumstances. I have first-hand experience myself. And that doesn’t change, though, that we stand in this amazing tradition of Anzac. I think one of the risks that we make over time is that we pretend that Anzacs in the past weren’t humans,” he said.

“But we’re all humans, we’re all imperfect, and none of us are above the law.”

The former Liberal prime minister John Howard made a similar point in a statement on Wednesday night, which argued that fundamental to the operation of the rule of law was that “no man or woman is above or beyond its reach”.

Some supporters of Roberts-Smith, including family members, have harboured resentment toward Hastie and believed he contributed to the Victoria Cross recipient’s downfall.

Guardian Australia last year revealed Roberts-Smith’s mother emailed Coalition MPs to warn that Hastie was “not fit” to lead the Liberal party as speculation swirled about his political aspirations.

On Thursday, Hastie said he didn’t have a problem, or a relationship, with Roberts-Smith, emphasising that he was subpoenaed to give evidence in the defamation trial.

The comments came as Katter, the independent MP for Kennedy, announced he would introduce a bill when parliament returns next month to protect the identity of veterans charged with crimes related to deployments in war.

The legislation would also mean such cases were heard by a jury made up of combat soldiers, who would judge the accused using “wartime standards”.

“Until he is proven guilty, I will stand 100% behind Ben just as I stand in solidarity with any person who has worn the uniform – anyone who has risked their life to defend Australia,” Katter said.

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