Most Christians would say that Bible condemns antisemitism. Yet, starting from second century all the way throughout middle ages all the way till 19-th century and even beginning of 20-th century antisemitism was a mainstream belief among Christians. So the question is why did things change? Yes, we have antisemites now, but nowdays they are a minority, while in the past they were vast majority. The typical Christian answer is that "they were not true Christians". But this doesn't address the question of a timeline. Why would Christians in the middle ages not be true Christians, while Christians in 21-st century be true Christians, when Bible prophesizes the opposite, that there would be falling away of the church at the end times.
I think the real honest reason why Christians have sympathy towards Jews is simply because they feel bad for the Jews after the holocaust. As much as Christians will deny it, this is something that objective look at the timeline, and objective use of secular psychology would tell us. And whether the Bible supports antisemitism or not is a separate question. I am not discussing whether Bible supports antisemitism -- I am only discussing the psychology of people that cause them to choose one interpretation of the Bible over the other. Right or wrong, it was traditional to choose antisemitic interpretations of the Bible. But then the holocaust made them feel bad for the Jews, so they decided to rethink their interpretation of the Bible and choose less antisemitic ones.
This being said, lets ask ourselves a different question. On the one hand, Christians can't bear the idea that 6 million holocaust victims deserved it. Yet, on the other hand, Christians are okay with an idea that people that are in hell deserve it. But you see, the 6 million Jews only suffered for limitted period of time, while hell suffering is eternal (the reason I say they suffered for limitted period of time is because Christians are not comfortable in saying Anne Frank or any other holocaust victim is in hell, even though they don't believe in Jesus; or even if we do say they are in hell, they would have been in hell with or without Hitler; the amount of suffering Hitler ADDED to it is finite). So why is it finite suffering of 6 million Jews is harder to bear than infinite suffering of a lot more people in hell? I think its because Christians haven't actually seen hell, yet they seen the suffering of 6 million Jews. Yes, they say they believe in hell. But its one thing to simply believe, and its another thing altogether to actually see it.
In fact lets ask ourselves a famous question as to how Hitler could go to heaven if he accepted Jesus right before his death and how Anne Frank could go to hell for not believing in Jesus. But, instead of trying to answer this question, lets ask ourselves a different question. Regardless if its true or not, why would it be more appealing to our sensitivities to see Anne Frank in heaven and Hitler in hell? In other words, we are not asking who is actually in heaven or in hell, we are only asking the question about ourselves: namely our own sensitivities. And it is a valid question. Because you see, if Anne Frank were to go to heaven and Hitler were to go to hell, then Hitler would suffer in hell a lot more and a lot longer than Anne Frank suffered in the real life. So, since the honest reason for sympathy towards Anne Frank is that she suffered more (see above), then this reason is no longer true, since now Hitler suffered more. Yet, I still claim that the reason that Anne Frank suffered more is real honest reason. Because, again, people haven't seen hell. So even though they conceptually know that Hitlers suffering in hell are a lot more severe and a lot longer, still deep down on a more intuitive level they feel that Anne Frank's suffering are worse, because its here in the tangible, while hell isn't.
A counter-argument to this is a statement "yes Hitler suffered more but he deserved it while Anne Frank didn't". I don't buy this either. Because one can claim that Jews deserved it too, since they killed Jesus. If you say "Romans killed Jesus", again, let me ask you to be honest with yourself and others. What would have happened if for the past 2 millenia people were to persecute Italians instead of Jews beause Romans killed Jesus, and then Hitler were to kill 6 millions Italians instead of 6 millions Jews for that same reason. Then everyone would feel bad for Italians and would say "Jews killed Jesus" not because they hate Jews but simply because they want to redeem Italians who were victims of all that persecution. But since in actuality it were the Jews that were persecutted and not the Italians, thats why nowdays so many people want to say that Romans killed Jesus out of sympathy towards Jews. But if we were to be more honest then yes Bible teaches Jews killed Jesus or at least strongly suggests it.
Then the other argument is that its unfair to nowdays Jews to be punished for what their ancestors did 2 millenia ago. Well, by the same token, it is also unfair to punish humankind as a whole for what Adam and Eve did in even more distant past. Yet, most Christians feel like punishing Jews for their ancestors is objectionable while the belief in original sin isn't. Again, I think it is because they wittnessed the holocaust so they feel a lot of sympathy towards the Jews. But wait a second: wouldn't the majority of mankind suffer for original sin a lot more severely and a lot longer than Jews suffered for the holocaust? Again: the holocaust happened in the tangible while the future hell for original sin isn't.
And also, as far as the idea that "unlike Anne Frank, it was Hitler's own choice", if you look at it from Calvinist perspective, Hitler was predestined to make the choices he did. I am not saying I am a Calvinist. But I can still ask a question: why is it, the people that are Calvinist, still act as if Hitler is responsible for what he did, yet Jews aren't responsible for how they were born, if neither of them had a choice (from Calvinist perspective)? Again, the answer lies in their sympathies towards Jews after the holocaust. And again I can ask why don't they have even more sympathies towards Hitler, given that he had no choice either (from their perspective), and he would suffer eternally? Again, the answer lies in the fact that they see Jewish suffering in the tangible while the suffering in hell is not tangible.
Now, if you look at all the bolded parts, you will see that the jist of why people changed their theology out of sympathy towards the holocaust victims yet they are okay in believing in hell and so forth, is really because, whether they admit it or not, they treat hell as less real than this tangible world. So the holocaust was really just a small glimpse of hell here in the tangible. And the glimpse of hell in the tagible is something they can't stand to the point of having to change their theology, while the full blown hell in the intangible is something they are willing to believe in, because even though they say they believe in it, deep down they treat it as intangible.
A lot of other social issues point to the same thing too. How come people are more mad at David Duke than they are at John Macarthur? David Duke never said Jews or blacks go to hell, he simply wants to change some policies here on earth, while John Macarthur says vast majority of people were predestined to hell from birth (even though this predestination is not related to skin color, how is it any better than if it was? whether its skin color or not, the bottom line is that they had no control over it). The reason David Duke is more offensive than John MacArthur is, again, because David Duke deals with the tangible while John Macarthur deals with intangible. People claim they treat hell as tangible, since they want to say they are Chrsitian. But the fact is they don't, as the above contrast illustrates.
By the way, I am a Christian. If you ask me what I believe Bible wants us to believe about those issues, I would be a lot more honest than most and say I don't know: Bible has many interpretations. But the above secular analysis should be considered, if you want to be honest with yourself.