I don't think that I specified religion as the only source of extremism. Was it the inclusion of witchcraft and the inquisition that led to this conclusion? Horror can be incubated in the womb of any form of extremism whether it be in the name of theism, deism, communism, fascism, or capitalism.Unfortunately the most extreme of the the Anti-Theist are still with us. Or shall we dredge up the genocide(s) of Stalin, Mao, and Pol-Pot? Those atrocities were committed in the last century yet they do not get mention from you in your historical listing. These murderers out committed the worthies (including if you wish to go back to the Crusades) of your list by about a score of 100 to 1.
Your premise is built of course in the belief that humanity is evolving to utopia. Genocides, murders, and atrocities are still with us and seem to be increasing in number not decreasing. The poor are still with us, racism it seems is still in play, and the human condition seems to be as static as it was 4000 years ago or so. What has been done is being repeated, it has not disappeared.
As a further historical note: the demise of slavery in the west was initiated by the worthy William Wilburforce, the noted British abolitionist and PM who also was an evangelical Christian. His work was mimicked by the American abolitionist(s) who were in the main American evangelicals who ran the underground railroad to Mary Beecher Stowe (who also advocated for emancipation for women). Your caricature withstanding, believers have been in the forefront of righting wrongs for good.
RAS
Lets talk about football okay?
Yes, civilization does evolve, just as does the biology of those who establish it. And, yes, with each generation, we discard some of the shackles that have resulted from the tyrannies of the past. Sometimes, we have reversions in which those whose ideas face rejection try to build dams across the currents of progress. It only provides a temporary lake that results in more rapid resolution once the dam breaks, often in the form of revolutions which could have been prevented had the attempts to reinforce the dam not been so visible.