For an interesting discussion of Islam, Judaism and Christianity from the personal perspective of three women, one from each faith, see
The Faith Club. It is this kind of dialogue that transcends simple tolerance to achieve understanding and learning that we need. As the reviewer writing in the link notes, however,
it is hard to achieve among people who are already convinced that their faith is the "one true faith".
How is that now? I believe that my faith is the one true faith, otherwise I wouldnt believe or practice it, although I'm highly tolerant of others views or choices, whether its got to do with religion as I understand it or anything else.
What we are looking at is the fragmentation of what was once a fairly monolithic religious establishment. For all the conflict that has ensued, it is a step in the right direction in the sense that people have choices, can disagree with church doctrine, can find the group that is the best fit, or start a new one, without being judged or penalized for heresy, etc. This reflects an essential shift of responsibility for one's spiritual life to the individual him/herself rather than clergy or the religious organization. I think Islam contains theory to support this, but it is not implemented or emphasized in practice much. Yes, far too many Christians still insist that theirs is the only correct religion, but most are willing to see other Christians as non-threatening, and entitled to their own beliefs and practice. Now to extend this to non-Christians and non-believers.
There's a lot in this single post which I would ask you to re-examine, although I'm not sure whether or not you would bother to do so.
The RCC, Christendom as it was prior to the reformation, was far from monolithic, there were diverse, disparite and warring or competiting factions before the reformation as there were afterwards. People always were able to dissent and begin different movements, the franciscans and groups like them are very good examples of how that happened.
The role of heresy and heresy hunting have been greatly exaggerated by years and years of anti-clerical propagandists and agitation, each seeking to air brush their own crimes out of the history books by exaggerating those of their opponents.
In reality the investigation of heresy was more akin to public enquiries which are still held today, yes the sentences handed down by clerical authorities were reflective of the superstition and standards of the time, which remains the case, if you look at some of the sentencing by secular authorities as late as the thirties and forties it is unlikely to seem that progressive. Consider McCarthyism.
In fact a lot of the practices commonly attributed to the church alone, such as torture, persecution and burnings or lynchings, were often popular or private measures, often practiced by barons, fuedal lords, monarchs, they acted often without fear or favour but the clerical authorities got the blame from history and posterity. In fact often the church's attempts to control practices such as these or curtail their just employment were the cause for the enmity which led those same national and regional powers and principalities to align themselves with rising protestantism.
The cimes of Calvin's Geneva were greater than the inquisition, deliberately so, as Calvin and his reformers felt the need to shock and awe their opposition, that's been repeated throughout history by secular revolutionaries and usurpers such as with the Paris Commune, the Smersh, NKVD, GRD etc. So it really is hard to draw a clear line and suggest that the inhumane and violent is the preserve of the religious, in particular those predating the reformation.
Islam has a pretty different structure in terms of authority and clerical and lay believer divisions, that's true, although that can be source of extremism and oppressive spontaneity in a manner that the alternative can not be. The sorts of mobilisation and mobilising capacities are mirrored in later secular atrocities too, such as the books about the actions of anti-semitic murder gangs in the second world war period, much of which was not ever directed or sanctioned by the Nazi party, if you'd like a book reference one I can think of is Hitler's Willing Executioners.
Handmaid's Tale may be fiction, but it is not implausible. Many aspects were present through the beginning of the last century, and some of the attitudes linger today. For real examples of fundamentalism in the US, just look at the Fundamentalist LDS (Mormon) church. Yes, they add their Book of Mormon to the Bible so are not Christian in the same sense as Methodists or Baptists. The point is that modern day Americans can be hoodwinked (i.e. raised) to tolerate and accept a very fundamentalist lifestyle.
I do think people can be hoodwinked, its often the people who flatter themselves that they are unlikely to be, Orwell wrote about this in reflection upon his use of the word IngSoc for the party ideology in 1984. He wrote to assure his readers that he was not opposed to the Labour Party or Socialism but that Ing Soc was an abbreviation for English Socialism and that it was meant to be a reference to his belief that fascism and totalitarianism would not go undisguised and would be likely to appear as something desirable and even demanded by the public.
So I would say that the while anyone could complain about the splitter in the eye of their perceived "useful idiots", ie the religious dupes adopting fundamentalism, they should instead guard against the conceit of their own views.
In the Handmaiden's Tale, if I remember rightly because I didnt like the book as much as I liked the film adaptation actually, there were numerous guerilla movements holding out against and fighting the regime which were Christian factions too, I think, as you say Methodists and Baptists, I read the pseudo-religious character of the regime in Handmaiden's Tale to be more about choosing a vehicle for patriarchal and establishment military figures. The whole thing seemed more masonic and like military fraternities as I know them.
In the US context I've always thought that the diversity and independence of some religious communities, such as the Amish, are positive and militate against totalitarianism, they dont want to see others conform to their precepts or principles but they are unlikely to adopt those of the wider society.
The same cant be said for a lot of liberal or libertarian political tendencies which view punitive consequences for dissenting from their precepts or principles as desirable.