Debate has been growing on Twitter as commentators line up to slam the French prosecutor in charge of the Germanwings crash investigation, after he said nothing suggested that the co-pilot of the A320 Airbus, which crashed into the French Alps killing all 150 people on board, was a terrorist.

"Nothing to suggest this was a terrorist act," Marseille prosecutor Brice Robin said in a press conference as he announced co-pilot Andreas Lubitz appears to have deliberately brought the plane down, but "voluntarily" manipulating the flight monitoring system.

This was later confirmed by the German authorities, according to AFP.

'Why in the world would Lubitz religion be relevant?'

In a blog post published soon after the German authorities declared Lubitz had "no apparent link to terrorist groups", Juan Cole, an American academic and Middle-East commentator, highlighted the question asked by a reporter during the press conference: "What was his religion?"

Germanwings' parent company Lufthansa said it didn't know, to which authorities added there was no evidence the crash was an act of "terrorism".

"Why in the world would his religion be relevant? If he did crash the plane on purpose then presumably he was depressed and wanted not only to commit suicide but also to be a mass murderer. It isn't political terrorism, likely, but certainly it was a terroristic act of killing," Cole wrote.

But we know why they asked, he continues. "It was out of bigotry against Muslims, probing whether another one had gone postal. The subtext is that white Christians don't go off the deep end, even though obviously they do, in large numbers. It isn't a logical question about Andreas Lubitz from Rhineland-Palatinate."

'They really do go by ethnicity it seems'

A growing number of online users have since taken to Twitter to criticise the authorities' decision to avoid using the term "terrorist" to describe the co-pilot.

Mike Spudgun, an award-nominated investigative journalist who has worked for ITV, Channel 4, BBC and SKY News, claimed that Lubitz should be described as a terrorist, adding that acts of terrorism are independent of religion.

Spudgun tweeted: "I don't care what religion Andreas Lubitz was. Anyone who slaughters 150 people is a f***ing terrorist, period".

Another journalist, Glenn Greenwald, who is a former columnist on civil liberties and US national security issues for the Guardian, pointed about how "different [the] coverage would be already if [the] co-pilot were Mohammed Al-Masaood, son of Egyptian immigrants".

In her tweet that was shared hundreds of time, a Libyan blogger who quoted media as saying "the tragic plane crash was an intentional act" but "the tragic plane crash was not an act of terrorism", wrote: "We read you loud and clear".

Libya Liberty then poked fun at the media covering the crash, writing: "Here, let me help you write your article", and posting a satirical graphic.

These views were echoed by Ali Abunimah, the co-founder of the Electronic Intifada – an independent online publication covering Middle-Eastern politics from a Palestinian perspective – who quoted the BBC as saying the pilot "was German. Not a known terrorist".

He added: "They really do go by ethnicity it seems".

Omar Suleiman, director of the Islamic Learning Foundation and an instructor at Mishkah University, also highlighted the media's coverage, tweeting: "The message from the media: Kill as many people as you want. As you as you're not Muslim, you won't be called a terrorist."

Al Jazeera's investigative reporter Clayton Swisher shared a tweet in which he also blamed "double standards" within media, who have described the co-pilot as either "disturbed" or "troubled".