My brother frequently demands a source when I tell an anecdote, then misuses Hitchen’s Razor to accuse me of making the anecdote up. This would be understandable if it was as a pics or it didn’t happen response to something outlandish, but it’s usually for something entirely mundane that was barely interesting enough to mention in the first place.
I don’t think their comment was pro-Iranian-post-revolutionary-government. The Shah was awful, was installed by the CIA, and did kill political opponents. US-backed governments don’t typically fall to revolutions, so a lot of people must have been upset to have enough of them to manage that. It’s generally accepted that what came after the revolution was worse, but it’s not just nutters, Stalinists and tankies that recognise it was also bad before, and got that way because the British wanted oil.
As far as I’m aware (which is a bit more than average as I’m British with an Iranian grandparent), both of you posted correct things. If the Shah hadn’t started killing anyone who disagreed with him, it would have been harder for the religious extremists to kill the rest. It’s not like you can ever assassinate all your political opponents as everyone knows other people, and those people don’t like their friends and family being murdered.