a pro-Iran person would like Fars News and take what they say to be the truth,
The funny thing is that Iran doesn't have anything close to something like Fox news (aka a mouthpiece to publish propaganda). Majority of these so called "mainstream media" in Iran which are being branded on Western platforms like Youtube as "state owned" are a bunch of dumb employees who blindly take the propaganda of the enemy and feed to google translate to publish on their outlet as news. It's actually quite funny sometimes, the way they do it

But I agree with what you are saying here, this is why I said you have to gain experience over time. You become familiar with the subject that interests you and in time you can figure out who is wrong and who is bullshitting. Who is right, and who is accurate. And although there is always bias, but there is a difference between being biased and spreading bullshit.
but I can't support them killing protesters just to retain power.
This is a good example of lack of diversifying sources and only relying on mouthpices.
I am assuming you are talking about the recent
1953-style of US-sponsored coup attempt in Iran where the US regime used terrorists to kill civilians. No it wasn't a protest. And no it wasn't Iranian government killing people to stay in power. It was US sponsored terrorists who were killing people who were trying to protest the fluctuating currency exchange rate the day before and who went back home when the terrorist attacks began.
Otherwise in a real protest, the (economic related) protesters don't burn down people's shops, bazars, hospitals, ambulance and fire trucks, mosques, libraries (specially the one that held ancient handwritten texts) and so on. We saw these things (specially attacking historical sites) in Syria by ISIS, aka another US sponsored terrorist organization.
For example the Rasht Bazar these US sponsored terrorists burnt down, wasn't just a place for trades, it was an ancient museum too.
And no these terrorists were not killed, because Iran is not US where the police is judge, jury and executioner. These US sponsored terrorists were arrested and their trials are still ongoing and they will receive the fair sentence they deserve (eg. those who committed murder will hang, other lesser crimes will face prison sentence, the "dumbasses" who were mixed into it not knowing this was a US sponsored coup attempt were already released).
So next time one of the Western mouthpieces said "Iranian government is killing protestors to remain in power" ask them why do those whom they refer to as "protester" carry US government issued machine guns, don't speak Farsi and enter crowded places like subway station to kill civilians.
The footage below belongs to Mashhad Metro station during the January 2026 terrorist attacks in Iran which they refer to as "protesters"!

Of course this is not the first time the US sponsored terrorists do something like this during the time Western mouthpieces are talking about "protests". Shiraz, 3 years ago:
https://www.aparat.com/v/W2qkO