I definitely agree somewhat...thunk the JKR trolls comparison is too harsh though.
I do get a bit fed up at the veneration of Tom Holland's book. He made good points but I do think some were a bit overstated. As we've said, Christianity definitely encourages better attitudes to slaves but it never forbids it. If Christianity is so intrinsically and unambiguously opposed to slavery, how come slavery was so widely permitted in Christendom until the early 19th century?
Similarly, democracy. Christianity is definitely more friendly to democracy than others but full democracy still only became widespread in Europe in the mid-20th century (think of places like France etc waiting until the 1940s to give women the vote).
I also think a lot of the effects of British Christianity are more characteristics of Britain rather than Christianity. This might sound a bit garbled - what I mean is that Christianity has had very different effects in different places. Attitudes to women in say, Mexico are different from attitudes in France. British colonialism, while brutal at times, was far far less so than French, German or Belgian. Yet these countries were all Christian. Obviously 20th century Ireland is a very disturbing example of Cathlocism getting out of hand in a way it hasn't in other Catholic countries, at least not to the same extent. Christianity did not prevent the rise of dictatorships and genocide in Germany, Italy, Spain etc in fact, in Spain for instance much of the Church cravenly kowtowed to Franco.
I suppose what I'm getting at is that Christianity has influenced all of Europe, and the very particular way Britain (or more specifically England) has developed isn't JUST applicable to Christianity, or even Protestant Christianity for that matter.