There actually has been a study along the lines of this article. It was done by studying the health of European monarchs, who by tradition have had millions of people praying for them every day and every week.
The attempt to excuse the Inquisition as less evil (by numeric count) than communisiom is amusing. It ignores the question of what a religion founded by Jesus was doing murdering and torturing people, and it ignores the question of why the religion itself didn't prevent it from happening.
Obviously theocracies can be evil, regardless of the nominal religion they spring from.
The attempt to excuse the Inquisition as less evil (by numeric count) than communisiom is amusing. It ignores the question of what a religion founded by Jesus was doing murdering and torturing people, and it ignores the question of why the religion itself didn't prevent it from happening.
Obviously theocracies can be evil, regardless of the nominal religion they spring from.
You asked and answered your own question. By definition, a non-coercive religion cannot "prevent" theocracies.
It's not a matter of count, but of the principles at work.
The idea driving the inquisition was that there was such a thing as a Christian commonwealth and that Christian profession was a requirement for full citizenship.
Lying about your religious profession in 16th century Spain was like sneaking over a border fence in 21st century America.
Illegally claiming citizenship under false pretenses.
In Stalin's Russia, simply disagreeing with the state's ideology was grounds for immediate execution, as was simply being inconvenient (i.e. being a kulak).
In inquisitorial Spain an openly professing Jew or Protestant was not subject to execution, but deportation instead. Servetus was deported from inquisitorial Spain - even though he openly denied the Trinity he was not executed but exiled. He was burned in Protestant Geneva.
Concealing one's religious allegiances was the capital crime.
Of course the numbers of murdered victims are far higher in the Stalinist regime, because the principles behind the punishment are different.
I don't think people should be tortured or hung for faking US citizenship, but that doesn't mean that I think it is wrong to have sanctions. Some will say it is cruel and arbitrary to sanction someone because they happen to have been born outside US territory, but all societies have to have limits for the sake of preserving public order.
And, to be clear, I am not justifying inqusitorial Spain. Good riddance to it. Just pointing out that there are different varieties of injustice.
I would also point out that inquisitorial Spain is a limit case among professing Christians for very specific historical reasons, whereas pretty much every officially atheist country in history has been awash in the blood of innocents.